Medicine - Cardiovascular Medicine

Bio

A Professor of Medicine who started his cardiology career at the USAF School of Aerospace Medicine performing cardiac screening of pilots, astronauts and military athletes. He is an international expert in clinical exercise physiology, ECGs, screening and the exercise sciences. He is a co-author of the textbook “Exercise and the Heart. Since 1992, he has been the major consultant to Stanford Sports Medicine and participated in the pre-participation exam of all Stanford athletes and professional teams in their care. He led the writing group for the first international document to specify the ECG criteria that lower the false positive rate for screening athletes for sudden cardiac death and has been a participant in the two Seattle Criteria meetings. He is a coauthor of a chapter in the Olympic Committee 2017 Cardiology Manual. He initiated the program of ECG screening at Stanford which is now mandated by the Athletic Department. He is now Director of the Sports Cardiology clinic with an office at the Falk Bldg in Cardiology and sees patients/athletes in the Cardiology Clinic area at Stanford Hospital and Clinics at 300 Pasteur Dr. Room A201B, Stanford, CA 94305.

Amateur Athletic HistoryHis amateur athletic experience includes lettering in collegiate tennis, playing intramural sports, running in slow 10k’s and over 15 Marathons. His “fastest” marathon was the “Avenue of the Giants” in under 3 hours. He has cycled down the coast to LA 4 times and used to climb Old La Honda often. As a person who enjoys exercise and competition, he has a profound appreciation and respect for everyone’s freedom to exercise to the intensity and level important to them whether they have a heart condition or not.

Contributions to Science* Sports Cardiology – For the past 22 years he has been the Cardiology Consultant for the Stanford Sports program and since 2015, the Director of the Stanford Sports Cardiology Clinic. His group has contributed to recent advancements in sports cardiology and has presented data regarding the application of ECG screening and of the cause of sudden cardiac death in athletes. * Screening of Asymptomatic USAF Aircrewmen – While Director of CV research and LtCol at the USAF School of Medicine (1972-1977), he presented seminal data on the angiographic findings and follow up of aircrewmen with abnormal ECGs and abnormal exercise tests. The Cardiovascular Effects of Cardiac Rehabilitation (PERFEXT) – While Director of Cardiac Rehabilitation at University Hospital and The San Diego VA (1977-1983), he was PI of an NHLBI funded randomized trial of Cardiac Rehabilitation. * Prognostic Studies in Veterans – While Chief of Cardiology at the LBVAMC, he developed the cardiology data bases for follow up studies of Veterans who had ECGs and exercise tests. The techniques perfected were the basis for the VETs treadmill studies and the ECG studies that are still on-going. These studies led to over 100 peer review publications in major journals and have led to clinical risk scores widely applied. * VA Co-operative Study of Quantitative Exercise Testing and Angiography (QUEXTA) He was the originator and Co PI for this study which applied computer techniques to both exercise testing and coronary angiography. It is seminal in that it also removed work up bias by only including patients with chest pain who agreed to both exercise testing and coronary angiography prior to any testing.

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Current Research and Scholarly Interests

Screening of athletes for sudden cardiac death, Computerized ECG and clinical data management; exercise Physiology including expired gas analysis; the effect of chronic and acute exercise on the heart; digitalrecording of biological signals; prognostic and diagnostic use of exercise testing; development of Expert Medical System software and educational tools.

Abstract

Sudden cardiac death (SCD) is the leading cause of mortality in athletes during sport. A variety of mostly hereditary, structural, or electrical cardiac disorders are associated with SCD in young athletes, the majority of which can be identified or suggested by abnormalities on a resting 12-lead electrocardiogram (ECG). Whether used for diagnostic or screening purposes, physicians responsible for the cardiovascular care of athletes should be knowledgeable and competent in ECG interpretation in athletes. However, in most countries a shortage of physician expertise limits wider application of the ECG in the care of the athlete. A critical need exists for physician education in modern ECG interpretation that distinguishes normal physiological adaptations in athletes from distinctly abnormal findings suggestive of underlying pathology. Since the original 2010 European Society of Cardiology recommendations for ECG interpretation in athletes, ECG standards have evolved quickly over the last decade; pushed by a growing body of scientific data that both tests proposed criteria sets and establishes new evidence to guide refinements. On 26-27 February 2015, an international group of experts in sports cardiology, inherited cardiac disease, and sports medicine convened in Seattle, Washington, to update contemporary standards for ECG interpretation in athletes. The objective of the meeting was to define and revise ECG interpretation standards based on new and emerging research and to develop a clear guide to the proper evaluation of ECG abnormalities in athletes. This statement represents an international consensus for ECG interpretation in athletes and provides expert opinion-based recommendations linking specific ECG abnormalities and the secondary evaluation for conditions associated with SCD.

Abstract

Sudden cardiac death is the leading cause of death in athletes. Long QT syndrome (LQTS) is one of the most common cardiogenetic diseases that can lead to sudden cardiac death and is identified by QT interval prolongation on an ECG. Recommendations for QT monitoring in athletes are adopted from nonathlete populations. To improve screening, ECG data of athletes are assessed to determine a more appropriate method for QT interval estimation.ECG (CardeaScreen) data were collected from June 2010 to March 2015. ECG data with HR greater than 100 bpm were excluded. Fiducial points of outliers were manually corrected if the QRS onset or the T wave offset was misidentified. A model of best fit was determined and compared across four QT correction factors. Classification analysis was used to compare the Bazett's corrected QT interval to the 99th percentile of uncorrected QT interval.High school (n = 597), college (n = 1207), and professional athletes (n = 273) (N = 2077) were analyzed. Mean age was 19 ± 3.5 yr. QT interval varied by cohort (HS = 388 ± 30, Col = 410 ± 33, Pro = 407 ± 27, p < 0.0001). A nonlinear power function with a cubic exponent of -0.349 fit the data the best (R = 0.64). Of the four common correction factors, Fridericia had the lowest residual dependence to HR (m = -0.10). With standard screening, 75% of athletes within the top 1% for QT interval were not identified for further investigation for LQTS.Up to 75% of athletes possessing an uncorrected QT interval greater than 99% of the population are not identified for investigation for LQTS using the recommended criteria. We propose a new method of risk stratification that replaces QT interval correction. Further study is needed to establish QT interval distributions and risk thresholds in athletes.

Abstract

Sudden cardiac death is often linked with hypertrophic cardiomyopathy in young athletes, but with a divergence of study results. We performed a meta-analysis to compare the prevalence of sudden cardiac deaths associated with hypertrophic cardiomyopathy vs sudden cardiac deaths associated with structurally normal hearts.A structured search of MEDLINE was conducted for studies published from 1990 through 2014. Retrospective cohort studies, patient registries, and autopsy series examining sudden cardiac death etiology in young individuals (age ≤35 years) were included. A random-effects model was applied to generate pooled summary estimates of the percentage of sudden cardiac deaths with structurally normal hearts at postmortem vs those caused by hypertrophic cardiomyopathy. Heterogeneity was assessed using I(2). Subgroup analyses were conducted based on study location, patient age groups, and population types.Thirty-four studies were included, representing a combined sample of 4605 subjects. The overall pooled percentage of sudden cardiac deaths caused by hypertrophic cardiomyopathy was 10.3% (95% confidence interval [CI], 8.0%-12.6%; I(2) = 87.2%), while sudden cardiac deaths with structurally normal hearts at death were more common (P

Abstract

The prognostic value of early repolarization with J waves and QRS slurs remains controversial. Although these findings are more prevalent in patients with idiopathic ventricular fibrillation, their ability to predict cardiovascular death has varied across studies.To test the hypothesis that J waves and QRS slurs on electrocardiograms (ECGs) are associated with increased risk for cardiovascular death.Retrospective cohort.Veterans Affairs Palo Alto Health Care System.Veterans younger than 56 years who had resting 12-lead electrocardiography, 90.5% of whom were men.Electrocardiograms were manually measured and visually coded using criteria of 0.1 mV or greater in at least 2 contiguous leads. J waves were measured at the peak of an upward deflection or notch at the end of QRS, and QRS slurs were measured at the top of conduction delay on the QRS downstroke. Absolute risk differences at 10 years were calculated to study the associations between J waves or QRS slurs and the primary outcome of cardiovascular death.Over a median follow-up of 17.5 years, 859 cardiovascular deaths occurred. Of 20 661 ECGs, 4219 (20%) had J waves or QRS slurs in the inferior and/or lateral territories; of these, 3318 (78.6%) had J waves or QRS slurs in inferior leads and 1701 (40.3%) in lateral leads. The upper bound of differences in risk for cardiovascular death from any of the J-wave or QRS slur patterns suggests that an increased risk can be safely ruled out (inferior, -0.77% [95% CI, -1.27% to -0.27%]; lateral, -1.07% [CI, -1.72% to -0.43%]).The study consisted of predominantly men, and deaths could be classified as cardiovascular but not arrhythmic.J waves and QRS slurs did not exhibit a clinically meaningful increased risk for cardiovascular death in long-term follow-up.None.

Abstract

To examine the prevalence of athletes who screen positive with the preparticipation examination guidelines from the American Heart Association, the AHA 12-elements, in combination with 3 screening electrocardiogram (ECG) criteria.Observational cross-sectional study.Stanford University Sports Medicine Clinic.Total of 1596 participants, including 297 (167 male; mean age, 16.2 years) high school athletes, 1016 (541 male; mean age, 18.8 years) collegiate athletes, and 283 (mean age, 26.3 years) male professional athletes.Athletes were screened using the 8 personal and family history questions from the AHA 12-elements. Electrocardiograms were obtained for all participants and interpreted using Seattle criteria, Stanford criteria, and European Society of Cardiology (ESC) recommendations.Approximately one-quarter of all athletes (23.8%) had at least 1 positive response to the AHA personal and family history elements. High school and college athletes had similar rates of having at least 1 positive response (25.9% vs 27.4%), whereas professional athletes had a significantly lower rate of having at least 1 positive response (8.8%, P < 0.05). Females reported more episodes of unexplained syncope (11.4% vs 7.5%, P = 0.017) and excessive exertional dyspnea with exercise (11.1% vs 6.1%, P = 0.001) than males. High school athletes had more positive responses to the family history elements when compared with college athletes (P < 0.05). The percentage of athletes who had an abnormal ECG varied between Seattle criteria (6.0%), Stanford criteria (8.8%), and ESC recommendations (26.8%).Many athletes screen positive under current screening recommendations, and ECG results vary widely by interpretation criteria.In a patient population without any adverse cardiovascular events, the currently recommended AHA 12-elements have an unacceptably high rate of false positives. Newer screening guidelines are needed, with fewer false positives and evidence-based updates.

Abstract

There is controversy regarding Q wave criteria for assessing risk for hypertrophic cardiomyopathy (HCM) in young athletes.The 12-lead ECGs from Preparticipation screening in healthy athletes and patients with HCM were studied retrospectively. All 12 leads were measured using the same automated ECG analysis program.There were a total of 225 HCM patients and 1124 athletes with 12-lead electrocardiograms available for analysis. Athletes were on average 20 years of age, 65% were male and 24% were African-American. Patients with HCM were on average 51 years of age, 56% were male and 5.8% were African-American. Q waves by either amplitude, duration or area criteria were more prevalent in males than females, in lateral leads than inferior and in HCM patients than athletes. The most striking difference in Q waves between the groups was in Limb lead I and in the females. Tall, skinny Q waves were rare in athletes and had the highest prevalence of only 3.7% in male HCM patients.Q waves are more common in males compared to females and in patients with HCM compared to athletes. Q waves of 30 ms or more in limb lead I appear to offer the greatest discriminatory value for separating patients with HCM from athletes.

Abstract

With diminishing time afforded to electrocardiography in the medical curriculum, we have found Sibbitt's simple mnemonic, the Diagonal Line Lead Rule, for a pattern recognition approach to 12-lead electrocardiogram (ECG) interpretation to be appreciated by students. However, it still lacks universal acceptance because its clinical utility has not been documented. The study objective was to demonstrate the clinical utility of the Diagonal Line Lead ECG Teaching Rule.After excluding ECGs of high-risk patients with Wolff-Parkinson-White syndrome and QRS durations greater than 120 ms, the initial ECGs of the remaining 43,798 patients were scored according to the Diagonal Line Lead Rule. A total of 45,497 patients from the Veterans Affairs Palo Alto Healthcare System were referred for a routine initial resting ECG from 1987 to 1999. We determined cardiovascular mortality with 8 years of follow-up.In patients with normal QRS duration, diagnostic Q-wave or T-wave inversions isolated to the diagonal line leads showed no increased risk of cardiovascular death. Q-wave or T-wave inversion in any other lead was significantly associated with cardiovascular death with an age-adjusted Cox hazard of 2.6 (confidence interval, 2.4-2.8; P < .0001) and an annual cardiovascular mortality rate of 3.0%. Leads V4-V6, I, and aVL were especially significant predictors of cardiovascular death, with a Cox hazard greater than 3.Our analysis demonstrates the prognostic power and clinical utility of a simple mnemonic for 12-lead ECG interpretation that can facilitate ECG teaching and interpretation.

Abstract

Controversy regarding adding the ECG to the evaluation of young athletes centers on the implications of false positives. Several guidelines have been published with recommendations for criteria to distinguish between ECG manifestations of training and markers of risk for cardiovascular (CV) sudden death. With an athlete dataset negative of any CV related abnormalities on follow-up, we applied three athlete screening criteria to identify the one with the lowest rate of abnormal variants.High school, college, and professional athletes underwent 12L ECGs as part of routine physicals. All ECGs were recorded and processed using CardeaScreen (Seattle, WA). The European (2010), Stanford (2011), and Seattle criteria (2013) were applied.From March 2011 to February 2013 1417 ECGs were collected. Mean age was 20±4years (14-35years), 36% female, 38.5% non-white (307 high school, 836 college and 284 professional). Rate of abnormal variants differed by criteria, predominately due to variation in interval thresholds for QT interval and QRS duration. There was a four-fold difference in abnormal variants between European and Seattle criteria (26% v 6%).The Seattle criterion was the most conservative resulting in 78% fewer abnormal variants than the European criteria. Variation was most evident with thresholds for QT prolongation, short QT interval, and intraventricular conduction delay. Continued research is needed to further understand normal training related adaptations and to improve modern ECG screening criteria for athletes.

Abstract

The significance of early repolarization, particularly regarding the morphology of the R-wave downslope, has come under question.We evaluated 29 281 resting ambulatory ECGs from the VA Palo Alto Health Care System. With PR interval as the isoelectric line and amplitude criteria ≥0.1 mV, ST-segment elevation is defined at the end of the QRS, J wave as an upward deflection, and slur as a conduction delay on the QRS downstroke. Associations of ST-segment elevation patterns, J waves, and slurs with cardiovascular mortality were analyzed with Cox analysis. With a median follow-up of 7.6 years, there were 1995 cardiac deaths. Of 29 281 subjects, 87% were male (55±14 years) and 13% were female (56±17 years); 13% were black, 6% were Hispanic, and 81% were white or other. Six hundred sixty-four (2.3%) had inferior or lateral ST-segment elevation: 185 (0.6%) in inferior leads and 479 (1.6%) in lateral leads, 163 (0.6%) in both, and 0.4% had global elevation. A total of 4041 ECGs were analyzed with enhanced display, and 583 (14%) had J waves or slurring, which were more prevalent in those with than in those without ST-segment elevation (61% versus 13%; P<0.001). ST-segment elevation occurred more in those with than in those without J waves or slurs (12% versus 1.3%; P<0.001). Except when involving only inferior leads, all components of early repolarization were more common in young individuals, male subjects, blacks, and those with bradycardia. All patterns and components of early repolarization were associated with decreased cardiovascular mortality, but this was not significant after adjustment for age.We found no significant association between any components of early repolarization and cardiac mortality.

Abstract

An "obesity paradox," in which overweight and obese individuals with established cardiovascular disease have a better prognosis than normal weight subjects, has been reported in a number of clinical cohorts, but little is known about the effects of weight loss on the obesity paradox and its association with health outcomes.Weight was determined in 3834 men at the time of a clinically referred exercise test and again during a clinical evaluation a mean of 7 years later. The associations among weight changes, baseline fitness, and other risk markers with cardiovascular and all-cause mortality were determined by Cox proportional hazards analysis.During the follow-up period, 314 subjects died (72 of cardiovascular causes). In a multivariate analysis (including baseline weight, weight change, exercise capacity, and cardiovascular disease), weight gain was associated with lower mortality and weight loss was associated with higher mortality (4% higher per pound lost per year, P

Abstract

While certain P-Wave morphologies have been associated with abnormal atrial size and either pulmonary or cardiovascular (CV) disease, their relationship to mortality and specific cause of death has not been reported.Analyses were performed on the first digitally recorded electrocardiogram (ECG) on 43 903 patients at the Palo Alto Veterans Administration Medical Center since 1987. After appropriate exclusions, 40 020 patients remained. Using computerized algorithms, P-wave amplitude and duration in 12 leads as well as several standardized ECG interpretations were extracted. The main outcome measures were pulmonary and CV mortality.During a mean follow-up of 6 years there were 3417 CV and 1213 pulmonary deaths. After adjusting for age and heart rate in a Cox regression model, P-wave amplitude in the inferior leads was the strongest predictor of pulmonary death (hazard ratio [HR]: 3.0, 95% confidence interval [CI]: 2.3-3.9, P < .0001 for an amplitude > 2.5 mm), outperforming all other ECG criteria. The depth of P-wave inversion in leads V(1) or V(2) and P-wave duration were strong predictors of CV death (HR: 1.7, 95% CI: 1.5-2.0, P < 0.0001 for a P-wave inversion deeper than 1 mm), outperforming many previously established ECG predictors of CV death.P-wave amplitude in the inferior leads is the strongest independent predictor of pulmonary death while P-wave duration and the depth of P-wave inversion in leads V(1) or V(2) significantly predict CV death. These measurements can be obtained easily and should be considered as part of clinical risk stratification.

Abstract

Inclusion of 12-lead electrocardiography (ECG) in preparticipation screening of young athletes is controversial because of concerns about cost-effectiveness.To evaluate the cost-effectiveness of ECG plus cardiovascular-focused history and physical examination compared with cardiovascular-focused history and physical examination alone for preparticipation screening.Decision-analysis, cost-effectiveness model.Published epidemiologic and preparticipation screening data, vital statistics, and other publicly available data.Competitive athletes in high school and college aged 14 to 22 years.Lifetime.Societal.Nonparticipation in competitive athletic activity and disease-specific treatment for identified athletes with heart disease.Incremental health care cost per life-year gained.Addition of ECG to preparticipation screening saves 2.06 life-years per 1000 athletes at an incremental total cost of $89 per athlete and yields a cost-effectiveness ratio of $42 900 per life-year saved (95% CI, $21 200 to $71 300 per life-year saved) compared with cardiovascular-focused history and physical examination alone. Compared with no screening, ECG plus cardiovascular-focused history and physical examination saves 2.6 life-years per 1000 athletes screened and costs $199 per athlete, yielding a cost-effectiveness ratio of $76 100 per life-year saved ($62 400 to $130 000).Results are sensitive to the relative risk reduction associated with nonparticipation and the cost of initial screening.Effectiveness data are derived from 1 major European study. Patterns of causes of sudden death may vary among countries.Screening young athletes with 12-lead ECG plus cardiovascular-focused history and physical examination may be cost-effective.Stanford Cardiovascular Institute and the Breetwor Foundation.

Abstract

Although the use of standardized cardiovascular (CV) system-focused history and physical examination is recommended for the preparticipation examination (PPE) of athletes, the addition of the electrocardiogram (ECG) has been controversial. Because the impact of ECG screening on college athletes has rarely been reported, we analyzed the findings of adding the ECG to the PPE of Stanford athletes.For the past 15 years, the Stanford Sports Medicine program has mandated a PPE questionnaire and physical examination by Stanford physicians for participation in intercollegiate athletics. In 2007, computerized ECGs with digital measurements were recorded on athletes and entered into a database.Although the use of standardized CV-focused history and physical examination are recommended for the PPE of athletes, the addition of the ECG has been controversial. Because the feasibility and outcomes of ECG screening on college athletes have rarely been reported, we present findings derived from the addition of the ECG to the PPE of Stanford athletes. For the past 15 years, the Stanford Sports Medicine program has mandated a PPE questionnaire and physical examination by Stanford physicians for participation in intercollegiate athletics. In 2007, computerized ECGs with digital measurements were recorded on athletes and entered into a database.Six hundred fifty-eight recordings were obtained (54% men, 10% African-American, mean age 20 years) representing 24 sports. Although 68% of the women had normal ECGs, only 38% of the men did so. Incomplete right bundle branch block (RBBB) (13%), right axis deviation (RAD) (10%), and atrial abnormalities (3%) were the 3 most common minor abnormalities. Sokolow-Lyon criteria for left ventricular hypertrophy (LVH) were found in 49%; however, only 27% had a Romhilt-Estes score of >or=4. T-wave inversion in V2 to V3 occurred in 7%, and only 5 men had abnormal Q-waves. Sixty-three athletes (10%) were judged to have distinctly abnormal ECG findings possibly associated with conditions including hypertrophic cardiomyopathy or arrhythmogenic right ventricular dysplasia/cardiomyopathy. These athletes were offered further testing but this was not mandated according to the research protocol.Six hundred fifty-three recordings were obtained (54% men, 7% African American, mean age 20 years), representing 24 sports. Although 68% of the women had normal ECGs, only 38% of the men did so. Incomplete RBBB (13%), RAD (10%), and atrial abnormalities (3%) were the 3 most common minor abnormalities. Sokolow-Lyon criteria for LVH were found in 49%; however, only 27% had a Romhilt-Estes score of >or=4. T-wave inversion in V2 to V3 occurred in 7% and only 5 men had abnormal Q-waves. Sixty-five athletes (10%) were judged to have distinctly abnormal ECG findings suggestive of arrhythmogenic right ventricular dysplasia, hypertrophic cardiomyopathy, and/or biventricular hypertrophy. These athletes will be submitted to further testing.Mass ECG screening is achievable within the collegiate setting by using volunteers when the appropriate equipment is available. However, the rate of secondary testing suggests the need for an evaluation of cost-effectiveness for mass screening and the development of new athlete-specific ECG interpretation algorithms.

Abstract

No matter how rare, the death of young athletes is a tragedy. Can it be prevented? The European experience suggests that adding the electrocardiogram (ECG) to the standard medical and family history and physical examination can decrease cardiac deaths by 90%. However, there has not been a randomized trial to demonstrate such a reduction. While there are obvious differences between the European and American experiences with athletes including very differing causes of athletic deaths, some would highlight the European emphasis on public welfare vs the protection of personal rights in the USA. Even the authors of this systematic review have differing interpretation of the data: some of us view screening as a hopeless battle against Bayes, while others feel that the ECG can save lives. What we all agree on is that the USA should implement the American Heart Association 12-point screening recommendations and that, before ECG screening is mandated, we need to gather more data and optimize ECG criteria for screening young athletes.

Abstract

Sudden cardiac death (SCD) is the leading cause of mortality in athletes during sport. A variety of mostly hereditary, structural or electrical cardiac disorders are associated with SCD in young athletes, the majority of which can be identified or suggested by abnormalities on a resting 12-lead electrocardiogram (ECG). Whether used for diagnostic or screening purposes, physicians responsible for the cardiovascular care of athletes should be knowledgeable and competent in ECG interpretation in athletes. However, in most countries a shortage of physician expertise limits wider application of the ECG in the care of the athlete. A critical need exists for physician education in modern ECG interpretation that distinguishes normal physiological adaptations in athletes from distinctly abnormal findings suggestive of underlying pathology. Since the original 2010 European Society of Cardiology recommendations for ECG interpretation in athletes, ECG standards have evolved quickly, advanced by a growing body of scientific data and investigations that both examine proposed criteria sets and establish new evidence to guide refinements. On 26-27 February 2015, an international group of experts in sports cardiology, inherited cardiac disease, and sports medicine convened in Seattle, Washington (USA), to update contemporary standards for ECG interpretation in athletes. The objective of the meeting was to define and revise ECG interpretation standards based on new and emerging research and to develop a clear guide to the proper evaluation of ECG abnormalities in athletes. This statement represents an international consensus for ECG interpretation in athletes and provides expert opinion-based recommendations linking specific ECG abnormalities and the secondary evaluation for conditions associated with SCD.

Abstract

Recent Expert consensus statements have sought to decrease false positive rates of electrocardiographic abnormalities requiring further evaluation when screening young athletes. These statements are largely based on traditional ECG patterns and have not considered computerized measurements.To define the normal limits for Q wave measurements from the digitally recorded ECGs of healthy young athletes.All athletes were categorized by sex and level of participation (high school, college, and professional), and underwent screening ECGs with routine pre-participation physicals, which were electronically captured and analyzed. Q wave amplitude, area and duration were recorded for athletes with Q wave amplitudes greater than 0.5mm at standard paper amplitude display (1mV/10mm). ANOVA analyses were performed to determine differences these parameters among all groups. A positive ECG was defined by our Stanford Computerized Criteria as exceeding the 99th percentile for Q wave area in 2 or more leads. Proportions testing was used to compare the Seattle Conference Q wave criteria with our data-driven criteria.2073 athletes in total were screened. Significant differences in Q wave amplitude, duration and area were identified both by sex and level of participation. When applying our Stanford Computerized Criteria and the Seattle criteria to our cohort, two largely different groups of athletes are identified as having abnormal Q waves.Computer analysis of athletes' ECGs should be included in future studies that have greater numbers, more diversity and adequate end points.

Abstract

Several studies suggest gender differences in ventricular dimensions in athletes. Few studies have, however, made comparisons of data indexed for lean body mass (LBM) using allometry. Ninety Caucasian college athletes (mixed sports) who were matched for age, ethnicity, and sport total cardiovascular demands underwent dual-energy x-ray absorptiometry scan for quantification of LBM. Athletes underwent comprehensive assessment of left and right ventricular and atrial structure and function using 2-dimensional echocardiography and deformation imaging using the TomTec analysis system. The mean age of the study population was 18.9 ± 1.9 years. Female athletes (n = 45) had a greater fat free percentage (19.4 ± 3.7%) compared to male athletes (11.5 ± 3.7%). When scaled to body surface area, male had on average 19 ± 3% (p <0.001) greater left ventricular (LV) mass; in contrast, when scaled to LBM, there was no significant difference in indexed LV mass -1.4 ± 3.0% (p = 0.63). Similarly, when allometrically scaled to LBM, there was no significant gender-based difference in LV or left atrial volumes. Although female athletes had mildly higher LV ejection fraction and LV global longitudinal strain in absolute value, systolic strain rate and allometrically indexed stroke volume were not different between genders (1.5 ± 3.6% [p = 0.63] and 0.0 ± 3.7% [p = 0.93], respectively). There were no differences in any of the functional atrial indexes including strain or strain rate parameters. In conclusion, gender-related differences in ventricular dimensions or function (stroke volume) appear less marked, if not absent, when indexing using LBM allometrically.

Abstract

We sought to characterize the prognostic value of the third universal definition of myocardial infarction (UDMI) and ≥40msec Q wave criteria.We evaluated hazard ratios (HR) with 95% confidence intervals (CI) for cardiovascular (CV) death for computerized Q wave measurements from the electrocardiograms of 43,661 patients collected from 1987 to 1999 at the Palo Alto VA. There were 3929 (9.0%) CV deaths over a mean follow-up of 7.6 (±3.8) years.The risk of CV death for Q waves ≥40msec in any two contiguous leads in any lead group was equivalent to or higher than that for contiguous UDMI Q waves, with HR 2.44 (95% CI 2.15-4.11) and HR 2.42 (95% CI (2.18-3.42), respectively.The UDMI Q wave criteria do not provide an advantage over ≥40msec Q waves at predicting CV death.

Abstract

Current guidelines for interpretation of the ECGs of athletes recommend that isolated R and S wave amplitudes that exceed traditional criteria for left ventricular hypertrophy be accepted as a physiological response to exercise training. This is based on training and echocardiographic studies but not on long term follow up. Demonstration of the prognostic characteristics of the amplitude criteria in a non-athletic population could support the current guidelines.To evaluate the prognostic value of the R and S wave voltage criteria for electrocardiographic left ventricular hypertrophy (ECG-LVH) in an ambulatory clinical population.The target population consisted of 20,903 ambulatory subjects who had ECGs recorded between 1987 and 1999 and were followed for cardiovascular death until 2013. During the mean follow up of 17years, there were 881 cardiovascular deaths.The mean age was 43±10, 91% were male and 16% were African American. Of the 2482 (12%) subjects who met the Sokolow-Lyon criteria, 241 (1.2%) subjects with left ventricular (LV) strain had an HR of 5.4 (95% CI 4.1-7.2, p<0.001), while 2241 (11%) subjects without strain had an HR of 1.4 (95% CI 1.2-1.8, p<0.001). Of the 4836 (23%) subjects who met the Framingham voltage criteria, 350 (2%) subjects with LV strain had an HR of 5.1 (95% CI 4.0-6.5, p<0.001), while 4486 (22%) subjects without strain had an HR of 1.1 (95% CI 0.9-1.3, p=0.26). The individual components of the Romhilt-Estes had HRs ranging from 1.4 to 3.6, with only the voltage component not being significant (HR 1.1, 95% CI 0.9-1.5, p=0.35).This study demonstrates that the R and S wave voltage criteria components of most of the original classification schema for electrocardiographic left ventricular hypertrophy are not predictive of CV mortality. Our findings support the current guidelines for electrocardiographic screening of athletes.

Abstract

Screening athletes with ECGs is aimed at identifying "at-risk" individuals who may have a cardiac condition predisposing them to sudden cardiac death. The Seattle criteria highlight QRS duration greater than 140 ms and ST segment depression in two or more leads greater than 50 μV as two abnormal ECG patterns associated with sudden cardiac death.High school, college, and professional athletes underwent 12 lead ECGs as part of routine pre-participation physicals. Prevalence of prolonged QRS duration was measured using cut-points of 120, 125, 130, and 140 ms. ST segment depression was measured in all leads except leads III, aVR, and V1 with cut-points of 25 μV and 50 μV.Between June 2010 and November 2013, 1595 participants including 297 (167 male, mean age 16.2) high school athletes, 1016 (541 male, mean age 18.8) college athletes, and 282 (mean age 26.6) male professional athletes underwent screening with an ECG. Only 3 athletes (0.2%) had a QRS duration greater than 125 ms. ST segment depression in two or more leads greater than 50 μV was uncommon (0.8%), while the prevalence of ST segment depression in two or more leads increased to 4.5% with a cut-point of 25 μV.Changing the QRS duration cut-point to 125 ms would increase the sensitivity of the screening ECG, without a significant increase in false-positives. However, changing the ST segment depression cut-point to 25 μV would lead to a significant increase in false-positives and would therefore not be justified.

Abstract

This report determines if the classic Romhilt-Estes score would predict better if points for its components were determined using a Cox hazard model and if the Cornell voltage criteria should replace the original criteria. Of the 20,903 subjects, the mean age was 43 ± 10 years and 90.6% were men. The mean follow-up for the population was 17 years, with 881 cardiovascular deaths; they were tested from 1987 to 1999 and followed until 2013. The new score was created with multipliers based on the Cox hazards of its elements with age bracket and gender included. The Cornell criteria were analyzed individually using Cox hazards with and without adjustments for age, gender, and African-American ethnicity and subsequently incorporated into the new score for analysis. For the new score, all 7 components were significant predictors of cardiovascular mortality with gender producing the greatest hazard ratio (HR) and left axis deviation and QRS duration >110 ms producing the lowest. For the original Romhilt-Estes score, 367 patients (1.8%) met the "definite" cutoff and had an HR of 5.6 (95% confidence interval 4.3 to 7.1). For the new score, 208 patients (1.0%) met the "definite" left ventricular hypertrophy cutoff and had an HR of 13.6 (95% confidence interval 10.8 to 17.3). The Romhilt-Estes had an area under the curve of 0.63, whereas the new score and new score with Cornell voltage both had an area under the curve of 0.7. In conclusion, our modified Romhilt-Estes score with new multipliers and without voltage criteria outperformed the original score.

Abstract

Abstract Sudden cardiac death (SCD) is the leading cause of death during exercise. While initial reports suggested that the most common cause of SCD in young athletes was due to hypertrophic cardiomyopathy (HCM), a critical review of investigations in several populations (athletes, non-athletes, military, national, and international) supports that the most common finding at autopsy of young individuals with SCD is actually a structurally normal heart (SNH). This information is vital for sports medicine clinicians, especially with regard to the pre-participation evaluation (PPE) since cardiac death associated with a SNH is likely attributed to disorders such as arrhythmia or ion channel diseases. This comprehensive review explores the causes of SCD, along with the symptoms preceding death, which ultimately may help refine the PPE and maximize the ability to detect potentially lethal disease prior to competition.

Abstract

Studies performed over the past 2 decades have supported the recommendation that the exercise test protocol be individualized and that a targeted duration of 8 to 12 minutes is optimal. However, this is not always implemented clinically because of the complication of having to choose a specific ramp to match a patient. We present a simple nomogram based on a questionnaire to choose 1 of 4 possible ramp protocols that provide individualized ramp rates for subjects undergoing clinical exercise testing.

Abstract

The third Universal Definition of Myocardial Infarction (UDMI) includes electrocardiographic criteria for ischemia, specifying horizontal or down-sloping ST depression ≥0.05 mV in two contiguous electrocardiogram (ECG) leads. We used the surrogate of cardiovascular (CV) death to evaluate the criteria.We collected computerized ST amplitude measurements, in different lead groupings, from the resting ECGs of 43,661 patients collected between 1987 and 1999 at the Palo Alto VA. There were 3929 (9.0%) cardiac deaths over a mean follow-up of 7.6 (SD 3.8) years.We found that horizontal or down-sloping ST depressions in contiguous leads, depending upon the lead groupings, had sensitivities ranging from 1% to 5%, specificities exceeding 99%, and relative risks for CV death ranging from 3.1 to 7.0 (p<0.001 for each individual relative risk) while horizontal or down-sloping ST depressions in a single lead had comparable values. We found that up-sloping ST depressions had greater sensitivities than horizontal or down-sloping ST depressions. Additionally, we found that ST depressions isolated to the inferior or anterior leads, without concomitant lateral depressions, were poor predictors of CV death.These findings reinforce and further characterize the value of ST depressions for predicting CV death. Furthermore, if these findings can be reproduced in the acute setting, they would undermine the requirement for contiguous lead depressions with slope assessment as well as prioritize ST depression in V4, V5, and V6 when assessing for myocardial ischemia.

Abstract

Despite recent concern about the significance of the J-wave pattern (also often referred to as early repolarization) and the importance of screening in athletes, there are limited rigorous prognostic data characterizing the 3 components of the J-wave pattern (ST elevation, J waves, and QRS slurs). We aim to assess the prevalence, patterns, and prognosis of the J-wave pattern among both stable clinical and athlete populations.We retrospectively studied 4,041 electrocardiograms from a multiethnic clinical population from 1997 to 1999 at the Veterans Affairs Palo Alto Health Care System. We also examined preparticipation electrocardiograms of 1,114 Stanford University varsity athletes from 2007 to 2008. Strictly defined criteria for components of the J-wave pattern were examined. In clinical subjects, prognosis was assessed using the end point of cardiovascular death after 7 years of follow-up.Components of the J-wave pattern were most prevalent in males; African Americans; and, particularly, athletes, with the greatest variations demonstrated in the lateral leads. ST elevation was the most common. Inferior J waves and slurs, previously linked to cardiovascular risk, were observed in 9.6% of clinical subjects and 12.3% of athletes. J waves, slurs, or ST elevation was not associated with time to cardiovascular death in clinical subjects, and ST-segment slope abnormalities were not prevalent enough in conjunction with them to reach significance.J waves, slurs, or ST elevation was not associated with increased hazard of cardiovascular death in our large multiethnic, ambulatory population. Even subsets of J-wave patterns, recently proposed to pose a risk of arrhythmic death, occurred at such a high prevalence as to negate their utility in screening.

Abstract

There is limited data describing ST segment amplitude in apparently healthy, asymptomatic populations. We analyzed ST amplitude in the standard resting electrocardiogram (ECG) in a large, multiethnic, stable, clinical population.We evaluated computerized ST amplitude measurements from the resting ECGs of 29,281 ambulatory outpatients collected between 1987 and 1999 at the Palo Alto, VA. With the PR interval as the isoelectric line, both elevation criteria (≥0.1 mV, ≥0.15 mV, and ≥0.2 mV) and depression criteria (≤-0.05 mV or ≤-0.1 mV), were applied. Cox-Hazard survival analysis techniques were used to demonstrate in which leads ST amplitude displacement was associated with cardiovascular (CV) death. To create a cohort without ECG patterns clearly associated with disease, we excluded ECGs with inverted T waves, wide QRS, or diagnostic Q waves and coded the remaining "normal" ECGs for ST elevation and depression to determine a normal range.The only ST amplitudes that were significantly and independently associated with time to CV death when adjusted for age, gender, and ethnicity were ST depression in all of the lateral leads (I, V4 -V6 ). When isolated to the inferior leads, (II and AVF), no ST amplitude criteria were associated with CV death. Among the "normal ECG" subgroup the precordial leads exhibited the greatest median ST amplitudes and the most significant differences between the leads, genders and ethnicities.Significant differences in ST amplitude were present in the precordial leads according to gender and ethnicity. This was particularly apparent when amplitude threshold were set for comparisons. Our findings provide the normal range for ST amplitude that when exceeded, should raise clinical concern.

Abstract

The study of J waves and slurs and their association with cardiovascular death is clouded by the lack of a standardized coding or classification methodology. Over the past three years of studying these ECG patterns, we have evolved a Data Entry Form that is designed to resolve some of the key issues. These issues include the effect of other ECG findings, whether the QRS-ST junction occurs before or after the J waves, if contiguous leads are required and rules to distinguish J waves from fragmented QRS complexes. This form is now being used to code the ECGs of 44,000 VA patients and the follow up is being extended to 15years to resolve these issues.

Abstract

In determining what is "abnormal"-in terms of cardiac electrical and morphologic remodeling in athletes-it is important to identify what is "normal" or expected. With specialization for each position in a football team lineup, we attempted to describe the association between the position played and the physiologic cardiac changes of designated players. We evaluated data from 85 National College Athletic Association football players from a single team. The participants were assigned to 1 of 3 groups based on position and training regimen: lineman (n = 34), mobility/power players (n = 13), and skill players (n = 38). Players underwent assessment with electrocardiography and echocardiography (ECHO), with results interpreted by reviewers blinded to players' positions. Linemen were found to have greater body mass index and body surface area (BSA), as well as longer QRS duration (102 ± 10 ms vs 101 ± 7 ms in mobility/power players, and 96 ± 7 ms in skill players; P < 0.007). Left ventricular (LV) voltage values were lower in linemen (27.7 ± 6.5 mV vs 28.8 ± 7 mV in mobility/power players, and 31.8 ± 7.6 mV in skill players; both, P < 0.05). No differences in ejection fraction between groups were revealed on ECHO, but ECHO did show greater calculated LV mass, LV end-diastolic diameter, aortic root diameter, and LV outflow tract diameter in linemen, whether adjusted for BSA or not, and the differences were statistically different. Multivariate analysis showed that position (P < 0.0004 and QRS duration (P = 0.03) predicted LV mass. Echocardiographic variables found to be associated with player position included LV mass adjusted for BSA (P < 0.0001), LV end-diastolic diameter adjusted for BSA (P < 0.0003), and QTc interval (P = 0.007). On multivariate analysis, racial identity did not demonstrate significant differences; however, differences existed on univariate analysis of electrocardiography and ECHO variables, mostly in skill players. In skill players, QRS duration was shorter in the African American (AA) subgroup compared with that in the white/other subgroup. Lateral ST elevation and LV end-systolic volume were greater in AA players after adjustment for BSA, and AA linemen had greater LV posterior wall thickness after adjustment for BSA. In summary, we found that football players who are linemen had greater heart mass than did other players, despite adjustments for body size.

Abstract

To augment data guiding thresholds for myocardial ischemia and cardiac risk, we studied resting ST amplitude in ambulatory patients and collegiate athletes.We analyzed 4041 ECGs from ambulatory visits at the Veterans Affairs in Palo Alto, California from 1997 to 1999 and 1114 screening ECGs from Stanford University athletes in 2007-2008. Using the PR interval as the isoelectric line and >95μV and

Abstract

Although extending the duration of ambulatory electrocardiographic monitoring beyond 24 to 48 hours can improve the detection of arrhythmias, lead-based (Holter) monitors might be limited by patient compliance and other factors. We, therefore, evaluated compliance, analyzable signal time, interval to arrhythmia detection, and diagnostic yield of the Zio Patch, a novel leadless, electrocardiographic monitoring device in 26,751 consecutive patients. The mean wear time was 7.6 ± 3.6 days, and the median analyzable time was 99% of the total wear time. Among the patients with detected arrhythmias (60.3% of all patients), 29.9% had their first arrhythmia and 51.1% had their first symptom-triggered arrhythmia occur after the initial 48-hour period. Compared with the first 48 hours of monitoring, the overall diagnostic yield was greater when data from the entire Zio Patch wear duration were included for any arrhythmia (62.2% vs 43.9%, p <0.0001) and for any symptomatic arrhythmia (9.7% vs 4.4%, p <0.0001). For paroxysmal atrial fibrillation (AF), the mean interval to the first detection of AF was inversely proportional to the total AF burden, with an increasing proportion occurring after 48 hours (11.2%, 10.5%, 20.8%, and 38.0% for an AF burden of 51% to 75%, 26% to 50%, 1% to 25%, and <1%, respectively). In conclusion, extended monitoring with the Zio Patch for ≤14 days is feasible, with high patient compliance, a high analyzable signal time, and an incremental diagnostic yield beyond 48 hours for all arrhythmia types. These findings could have significant implications for device selection, monitoring duration, and care pathways for arrhythmia evaluation and AF surveillance.

Abstract

Electrocardiographic changes in athletes are common and usually reflect benign structural and electrical remodelling of the heart as a physiological adaptation to regular and sustained physical training (athlete's heart). The ability to identify an abnormality on the 12-lead ECG, suggestive of underlying cardiac disease associated with sudden cardiac death (SCD), is based on a sound working knowledge of the normal ECG characteristics within the athletic population. This document will assist physicians in identifying normal ECG patterns commonly found in athletes. The ECG findings presented as normal in athletes were established by an international consensus panel of experts in sports cardiology and sports medicine.

Abstract

Cardiac channelopathies are potentially lethal inherited arrhythmia syndromes and an important cause of sudden cardiac death (SCD) in young athletes. Other cardiac rhythm and conduction disturbances also may indicate the presence of an underlying cardiac disorder. The 12-lead ECG is utilised as both a screening and a diagnostic tool for detecting conditions associated with SCD. Fundamental to the appropriate evaluation of athletes undergoing ECG is an understanding of the ECG findings that may indicate the presence of a pathological cardiac disease. This article describes ECG findings present in primary electrical diseases afflicting young athletes and outlines appropriate steps for further evaluation of these ECG abnormalities. The ECG findings defined as abnormal in athletes were established by an international consensus panel of experts in sports cardiology and sports medicine.

Abstract

Cardiomyopathies are a heterogeneous group of heart muscle diseases and collectively are the leading cause of sudden cardiac death (SCD) in young athletes. The 12-lead ECG is utilised as both a screening and diagnostic tool for detecting conditions associated with SCD. Fundamental to the appropriate evaluation of athletes undergoing ECG is an understanding of the ECG findings that may indicate the presence of an underlying pathological cardiac disorder. This article describes ECG findings present in cardiomyopathies afflicting young athletes and outlines appropriate steps for further evaluation of these ECG abnormalities. The ECG findings defined as abnormal in athletes were established by an international consensus panel of experts in sports cardiology and sports medicine.

Abstract

Sudden cardiac death (SCD) is the leading cause of death in athletes during sport. Whether obtained for screening or diagnostic purposes, an ECG increases the ability to detect underlying cardiovascular conditions that may increase the risk for SCD. In most countries, there is a shortage of physician expertise in the interpretation of an athlete's ECG. A critical need exists for physician education in modern ECG interpretation that distinguishes normal physiological adaptations in athletes from abnormal findings suggestive of pathology. On 13-14 February 2012, an international group of experts in sports cardiology and sports medicine convened in Seattle, Washington, to define contemporary standards for ECG interpretation in athletes. The objective of the meeting was to develop a comprehensive training resource to help physicians distinguish normal ECG alterations in athletes from abnormal ECG findings that require additional evaluation for conditions associated with SCD.

Abstract

The addition of the ECG to the preparticipation examination (PPE) of high school athletes has been a topic for debate. Defining the difference between the high school male and female ECG is crucial to help initiate its implementation in the High School PPE. Establishing the different parameters set for the male and female ECG would help to reduce false positives. We examined the effect of gender on the high school athlete ECG by obtaining and analyzing ECG measurements of high school athletes from Henry M. Gunn High School.In 2011 and 2012, computerized Electrocardiograms were recorded and analyzed on 181 athletes (52.5% male; mean age 16.1 ± 1.1 years) who participated in 17 different sports. ECG statistics included intervals and durations in all 3 axes (X, Y, Z) to calculate 12 lead voltage sums, QRS Amplitude, QT interval, QRS Duration, and the sum of the R wave in V5 and the S Wave in V2 (RS Sum).By computer analysis, we demonstrated that male athletes had significantly greater QRS duration, Q-wave duration, and T wave amplitude. (P<0.05). By contrast, female athletes had a significantly greater QTc interval. (P<0.05).The differences in ECG measurements in high school athletes are strongly associated with gender. However, body size does not correlate with the aforementioned ECG measurements. Our tables of the gender-specific parameters can help facilitate the development of a more large scale and in-depth ECG analysis for screening high school athletes in the future.

Abstract

Though early repolarization (ER) in the inferior leads has been associated with increased cardiovascular risk, its natural history is uncertain. We aimed to study the serial electrocardiographic behavior of inferior ER and understand factors associated with that behavior.We selected electrocardiograms (ECGs) from patients with the greatest amplitude of ER in AVF from ECGs of 29,281 ambulatory patients recorded between 1987 and 1999 at the Palo Alto Veterans Affairs Hospital. Starting from the highest amplitude, we reviewed the ECGs and medical records from the first 85%. From this convenience sample, 36 were excluded for abnormal patterns similar to ER. The remaining 257 patients were searched for another ECG at least 5 months later, of whom, 136 satisfied this criteria. These ECGs were paired for comparison and coded by four interpreters.The average time between the first and second ECGs was 10 years. Of the 136 subjects, 47% retained ER while 53% no longer fulfilled the amplitude criteria. While no significant differences were found in initial heart rate (HR) or time interval between ECGs, those who lost the ER pattern had a greater difference in HR between the ECGs. There was no significant difference in the incidence of cardiovascular events or deaths.In conclusion, the ECG pattern of ER was lost over 10 years in over half of the cohort. The loss of ER was partially explained by changes in HR, but not higher incidence of cardiovascular events or death, suggesting the entity is a benign finding.

Abstract

To evaluate the prevalence of early polarization (ER) in a stable population and to evaluate the prognostic significance of the association or absence of Q waves or T-wave inversion (TWI).In this retrospective study performed at the university-affiliated Palo Alto Veterans Affairs Health Care Center from March 1, 1987, through December 31, 1999, we evaluated outpatient electrocardiograms. Vital status and cause of death were determined in all patients, with a mean ± SD follow-up of 7.6±3.8 years.Of the 29,281 patients, 87% were men and 13% were African American. Inferior or lateral ER was present in 664 patients (2.3%): in inferior leads in 185 (0.6%), in lateral leads in 479 (1.6%) , and in both inferior and lateral leads in 163 (0.6%). Only when Q waves or TWI accompanied ER was there an increased risk of cardiovascular death (Cox proportional hazards regression model, 5.0; 95% confidence interval, 3.4-7.2; P

Abstract

Increased prevalence of classic early repolarization, defined as ST-segment elevation (STE) in the absence of acute myocardial injury, in African Americans is well established. The prognostic value of this pattern in different ethnicities remains controversial.Measure association between early repolarization and cardiovascular mortality in African Americans.The resting electrocardiograms of 45,829 patients were evaluated at the Palo Alto Veterans Affairs Hospital. Subjects with inpatient status or electrocardiographic evidence of acute myocardial infarction were excluded, leaving 29,281 subjects. ST-segment elevation, defined as an elevation of >0.1 mV at the end of the QRS, was electronically flagged and visually adjudicated by 3 observers blinded to outcomes. An association between ethnicity and early repolarization was measured by using multivariate logistic regression. We analyzed associations between early repolarization and cardiovascular mortality by using the Cox proportional hazards regression analysis.Subjects were 13% women and 13.3% African Americans, with an average age of 55 years and followed for an average of 7.6 years, resulting in 1995 cardiovascular deaths. There were 479 subjects with lateral STE and 185 with inferior STE. After adjustment for age, sex, heart rate, and coronary artery disease, African American ethnicity was associated with lateral or inferior STE (odds ratio 3.1; P = .0001). While lateral or inferior STE in non-African Americans was independently associated with cardiovascular death (hazard ratio 1.6; P = .02), it was not associated with cardiovascular death in African Americans (hazard ratio 0.75; P = .50).Although early repolarization is more prevalent in African Americans, it is not predictive of cardiovascular death in this population and may represent a distinct electrophysiologic phenomenon.

Abstract

Broad criteria for abnormal electrocardiogram (ECG) findings, requiring additional testing, have been recommended for preparticipation exams (PPE) of athletes. As these criteria have not considered the sport in which athletes participate, we examined the effect of sports on the computerized ECG measurements obtained in college athletes.During the Stanford 2007 PPE, computerized 12-lead ECGs (Schiller AG) were obtained in 641 athletes (350 male/291 female, age 19.5 ± 2 years). Athletes were engaged in 22 different sports and were grouped into 16 categories: baseball/softball, basketball, crew, crosscountry, fencing, field events, football linemen, football other positions, golf, gymnastics, racquet sports, sailing, track/field, volleyball, water sports, and wrestling. The analysis focused on ECG leads V2, aVF and V5 which provide a three-dimensional representation of the heart's electrical activity. As marked ECG differences exist between males and females, the data are presented by gender.In males, ANOVA analysis yielded significant ECG differences between sports for heart rate, QRS duration, QTc, J-amplitude in V2 and V5, spatial vector length (SVL) of the P wave, SVL R wave, and SVL T wave, and RS(sum) (p

Abstract

Although it is known that the electrocardiographic pattern of early repolarization (ER) occurs most commonly in healthy young bradycardic men, its natural history is uncertain. We considered initial electrocardiograms (ECGs) at rest from 29,281 ambulatory patients recorded from 1987 through 1999 at Veterans Affairs Palo Alto Hospital. With PR interval as the isoelectric line and amplitude criterion as >0.1 mV ER was identified when any of the following fulfilled the amplitude criterion: ST-segment elevation at the end of the QRS duration, J waves as an upward deflection, and slurs as delay on the R wave downstroke. The first 250 ECGs with the greatest ER increase were selected and the database was searched for an ECG >5 months later. Of the 250 patients selected with the greatest amplitude of ER 6 were excluded for electrocardiographic abnormalities, leaving 244 subjects, of whom 122 had another ECG ≥5 months later. Their average age was 42 ± 10 years and average time from the first to second ECG was 10 years. Of the 122 patients 47 (38%) retained ER, whereas most (62%) no longer fulfilled the amplitude criterion. There were no significant differences in heart rate or time interval between ECGs. In conclusion, the electrocardiographic pattern of ER was lost over 10 years in more than half of this young clinical cohort and the loss was not caused by higher heart rate, longer time between ECGs, decrease in R-wave amplitude, death, acute disease, or alterations in electrocardiographic diagnostic characteristics.

Abstract

To demonstrate the prevalence and patterns of ST elevation (STE) in ambulatory individuals and athletes and compare the clinical outcomes.Retrospective cohort study. ST elevation was measured by computer algorithm and defined as ≥0.1 mV at the end of the QRS complex. Elevation was confirmed, and J waves and slurring were coded visually.Veterans Affairs Palo Alto Health Care System and Stanford University varsity athlete screening evaluation.Overall, 45 829 electrocardiograms (ECGs) were obtained from the clinical patient cohort and 658 ECGs from athletes. We excluded inpatients and those with ECG abnormalities, leaving 20 901 outpatients and 641 athletes.Electrocardiogram evaluation and follow-up for vital status.All-cause and cardiovascular mortality and cardiac events.ST elevation in the anterior and lateral leads was more prevalent in men and in African Americans and inversely related to age and resting heart rate. Athletes had a higher prevalence of early repolarization even when matched for age and gender with nonathletes. ST elevation greater than 0.2 mV (2 mm) was very unusual. ST elevation was not associated with cardiac death in the clinical population or with cardiac events or abnormal test results in the athletes.Early repolarization is not associated with cardiac death and has patterns that help distinguish it from STE associated with cardiac conditions, such as myocardial ischemia or injury, pericarditis, and the Brugada syndrome.

Abstract

Exercise-induced left bundle branch block (EI-LBBB) is an infrequent finding. Its prevalence and prognostic significance are not clear.To evaluate, in a longitudinal study, the prevalence and prognostic significance of EI-LBBB in American war veterans.We evaluated 9,623 patients submitted to an exercise test (ET) in treadmill between 1987 and 2007. The outcomes were compared between those with normal TE, the ones with EI-LBBB and the ones with down-sloping ST-segment. Mortality and causes of death were identified while blinded to the ET results.In this prospective cohort, 6,922 individuals had normal ET results (57.2 ± 11.4 years), 1,739 had abnormal ST-segment depression (62.7 ± 9.8 years), and 38 had EI-LBBB (65.2 ± 11.9 years). The prevalence of EI-LBBB was 0.38%. After 8.8 years, there were 1,699 deaths due to all-cause mortality and 610 cardiovascular (CV) deaths; coronary artery disease and heart failure were more prevalent in patients with EI-LBBB. Patients with EI-BCRE had a hazard ratio of 2.37 (p = 0.002) for all-cause mortality, but it was not significant when adjusted for age or when the CV death was the assessed outcome.EI-LBBB is a rare clinical finding. Individuals with BCRE-EI have higher all-cause mortality when compared to those with normal ET results. However, this fact is explained by the fact that these patients are significantly older and have more associated cardiovascular diseases.

Abstract

Cardiac repolarization adaptation to cycle length change is patient dependent and results in complex QT-RR hysteresis. We hypothesize that accurate patient-specific QT-RR curves and rate corrected QT values (QTc) can be derived through patient-specific modeling of hysteresis.Model development was supported by QT-RR observations from 1959 treadmill tests, allowing extensive exploration of the influences of autonomic function on QT adaptation to rate changes. The methodology quantifies and then removes patient-specific repolarization adaptation rates. The estimated average 95% QT confidence limit was approximately 1 msec for the studied population. The model was validated by comparing QT-RR curves derived from a submaximal exercise protocol with rapid exercise and recovery phases, characterized by high hysteresis, with QT-RR values derived from an incremental stepped protocol that held heart rate constant for 5 minutes at each stage of exercise and recovery.The underlying physiologic changes affecting QT dynamics during the transitions from rest to exercise to recovery are quite complex. Nevertheless, a simple patient-specific model, comprising only three parameters and based solely on the preceding history of RR intervals and trend, is sufficient to accurately model QT hysteresis over an entire exercise test for a diverse population. A brief recording of a resting ECG, combined with a short period of submaximal exercise and recovery, provides sufficient information to derive an accurate patient-specific QT-RR curve, eliminating QTc bias inherent in population-based correction formulas.

Abstract

Sudden cardiac death in athletes is rare but has a wide social impact because it confronts the general population with the paradox that athletes perceived and admired as the fittest and healthiest suddenly drop dead during their sport. Mass media coverage is guaranteed in the case of sudden cardiac death of a top athlete, while other competitive and noncompetitive athletes of all ages, team members, sponsors, as well as huge parts of society remain puzzled and frightened. Therefore, debate is ongoing regarding how to minimize the number of fatalities, and the search continues for a cost-effective preparticipation screening for competitive athletes. Despite the fact that routine ECG screening would be widely available and rather inexpensive, debate continues regarding whether this should be part of initial screening for every athlete before starting to train at high intensity as well as during annual checkups. The role of ECGs in preparticipation examinations of competitive athletes is intensively discussed because there is a lack of strict criteria for which ECG findings should generate further workup. In this article, we analyze the main publications on sudden cardiac death, focusing on the benefit of ECG screening in preparticipation examination as it has been shown to be feasible and effective in identifying athletes at risk of sudden cardiac death.

Abstract

Background Broad criteria for classifying an electrocardiogram (ECG) as abnormal and requiring additional testing prior to participating in competitive athletics have been recommended for the preparticipation examination (PPE) of athletes. Because these criteria have not considered gender differences, we examined the effect of gender on the computerized ECG measurements obtained on Stanford student athletes. Currently available computer programs require a basis for "normal" in athletes of both genders to provide reliable interpretation. Methods During the 2007 PPE, computerized ECGs were recorded and analyzed on 658 athletes (54% male; mean age, 19 +/- 1 years) representing 22 sports. Electrocardiogram measurements included intervals and durations in all 12 leads to calculate 12-lead voltage sums, QRS amplitude and QRS area, spatial vector length (SVL), and the sum of the R wave in V5 and S wave in V2 (RSsum). Results By computer analysis, male athletes had significantly greater QRS duration, PR interval, Q-wave duration, J-point amplitude, and T-wave amplitude, and shorter QTc interval compared with female athletes (all P < 0.05). All ECG indicators of left ventricular electrical activity were significantly greater in males. Although gender was consistently associated with indices of atrial and ventricular electrical activity in multivariable analysis, ECG measurements correlated poorly with body dimensions. Conclusion Significant gender differences exist in ECG measurements of college athletes that are not explained by differences in body size. Our tables of "normal" computerized gender-specific measurements can facilitate the development of automated ECG interpretation for screening young athletes.

Abstract

A graded but nonlinear relationship exists between fitness and mortality, with the greatest mortality differences occurring between the least-fit (first, Q1) and the next-least-fit (second, Q2) quintiles of fitness. The purpose of this study was to compare clinical characteristics, exercise test responses, and physical activity (PA) patterns in Q1 versus Q2 in patients with cardiovascular disease (CVD).Observational retrospective study.A total of 5101 patients with a history of CVD underwent clinical treadmill testing and were followed up for 9.1+/-5.5 years. Patients were classified into quintiles of exercise capacity measured in metabolic equivalents. Clinical characteristics, treadmill test results, and recreational PA patterns were compared between Q1 (n = 923) and Q2 (n = 929).Q1 had a nearly two-fold increase in age-adjusted relative risk of cardiovascular mortality compared with Q2 (hazard ratio: 3.79 vs. 2.04, P<0.05; reference: fittest quintile). Q1 patients were older, had more extensive use of medications, and were more likely to have a history of typical angina (35 vs. 28%), myocardial infarction (30 vs. 24%), chronic heart failure (25 vs. 14%), claudication (15 vs. 9%) and stroke (9 vs. 6%) compared with Q2 (all comparisons: P<0.05). Recent and lifetime recreational PA was not different between the two groups.Greater severity of disease in the least-fit versus the next-least-fit quintile likely contributes to but cannot fully explain marked differences in mortality rates in CVD patients. To achieve potential survival benefits, our results suggest that unfit CVD patients should engage in exercise programs of sufficient volume and intensity to improve fitness.

Abstract

Premature ventricular contractions (PVC) at rest are frequently seen in heart failure (HF) patients but conflicting data exist regarding their importance for cardiovascular (CV) mortality. This study aims to evaluate the prognostic value of rest PVCs on an electrocardiogram (ECG) in patients with a history of clinical HF.We considered 352 patients (64 + or - 11 years; 7 females) with a history of clinical HF undergoing treadmill testing for clinical reasons at the Veterans Affairs Palo Alto Health Care System (VAPAHCS) (1987-2007). Patients with rest PVCs were defined as having > or = 1 PVC on the ECG prior to testing (n = 29; 8%). During a median follow-up period of 6.2 years, there were 178 deaths of which 76 (42.6%) were due to CV causes. At baseline, compared to patients without rest PVCs, those with rest PVCs had a lower ejection fraction (EF) (30% vs 45%) and the prevalence of EF < or = 35% was higher (75% vs 41%). They were more likely to have smoked (76% vs 55%).The all-cause and CV mortality rates were significantly higher in the rest PVCs group (72% vs 49%, P = 0.01 and 45% vs 20%, P = 0.002; respectively). After adjusting for age, beta-blocker use, rest ECG findings, resting heart rate (HR), EF, maximal systolic blood pressure, peak HR, and exercise capacity, rest PVC was associated with a 5.5-fold increased risk of CV mortality (P = 0.004). Considering the presence of PVCs during exercise and/or recovery did not affect our results.The presence of PVC on an ECG is a powerful predictor of CV mortality even after adjusting for confounding factors.

Abstract

While the role of hemoglobin in heart failure and renal disease has been investigated, little is known about its effect on clinical exercise test performance and mortality in patients referred for routine exercise treadmill testing (ETT).Patients with low hemoglobin will have poor exercise capacity and would be at increased risk of mortality and cardiovascular (CV) events.Clinical variables, laboratory values, and exercise treadmill data were obtained for 1,799 patients referred for routine ETT from 1997 to 2004. All-cause mortality was obtained from the United States Social Security death index and autopsy reports or clinical notes were used to determine CV events and mortality. P values < 0.05 were considered significant.Our population had a mean age of 58 +/- 12 years, 16% had diabetes, 53% had hypertension, 35% had hypercholesterolemia, and 67% had a history of smoking. During follow-up, 10.3% of patients died, 3.9% of patients died of CV causes, and 11.6% had cardiovascular events. Anemic patients (hemoglobin [Hgb] < 13 g/dL) achieved lower metabolic equivalents (METs) than nonanemic patients and had more ST-segment depression (15.5% versus 8.6%, p < 0.004). Proportional hazard analysis demonstrated that hemoglobin was significantly associated with all-cause mortality (p < 0.0007), CV mortality (p < 0.009), and CV events (p < 0.01). Kaplan-Meier survival analysis demonstrated that anemic patients had significantly higher mortality and CV events.Hemoglobin is significantly associated with exercise performance, ST-segment depression during ETT, mortality, and cardiovascular events. The incorporation of hemoglobin may add diagnostic and prognostic information to ETT.

Abstract

Atrial fibrillation (AF) is the most prevalent arrhythmia in the United States and accounts for more than 750,000 strokes per year. Noninvasive predictors of AF may help identify patients at risk of developing AF. Our objective was to identify the electrocardiographic characteristics associated with onset of AF.This was a retrospective cohort analysis of 42,751 patients with electrocardiograms (ECGs) ordered by physician's discretion and analyzed using a computerized system. The population was followed for detection of AF on subsequent ECGs. Cox proportional hazard regression analysis was performed to test the association between these ECG characteristics and development of AF.For a mean follow-up of 5.3 years, 1,050 (2.4%) patients were found to have AF on subsequent ECG recordings. Several ECG characteristics, such as P-wave dispersion (the difference between the widest and narrowest P waves), premature atrial contractions, and an abnormal P axis, were predictive of AF with hazard ratio of approximately 2 after correcting for age and sex. P-wave index, the SD of P-wave duration across all leads, was one of the strongest predictors of AF with a concordance index of 0.62 and a hazard ratio of 2.7 (95% CI 2.1-3.3) for a P-wave index >35. These were among the several independently predictive markers identified on multivariate analysis.Several ECG markers are independently predictive of future onset of AF. The P index, a measurement of disorganized atrial depolarization, is one of the strongest predictors of AF. The ECG contains valuable prognostic information that can identify patients at risk of AF.

Abstract

The exercise electrocardiogram (ECG) is widely considered the best available test for screening asymptomatic adults without known cardiovascular (CV) disease prior to initiating a vigorous exercise programme due to its prognostic value, widespread availability and low cost. Observational studies have demonstrated an increased relative risk of CV events with positive screening exercise ECG tests in men with diabetes, advanced age, or multiple cardiac risk factors. Recent observational studies have not demonstrated similar prognostic value for exercise ECG testing in asymptomatic healthy women. Despite the predictive ability of exercise ECG testing in several groups, there have been no studies demonstrating a significant impact of screening on morbidity and mortality in completely asymptomatic patients, leading to significant discordance in consensus guidelines on screening. One prospective observational study is ongoing in Italy that may for the first time demonstrate the ability to decrease incident CV events using preparticipation screening exercise ECG testing in adult athletes with targeted exclusion from athletics. Until more conclusive data is available the authors currently recommend screening exercise ECG testing in asymptomatic men with diabetes and asymptomatic men over age 45 with two or more CV risk factors prior to initiating a vigorous exercise programme. Consideration should also be given to screening asymptomatic patients younger than 45 with particularly strong risk factor exposure or elderly patients with fewer than two risk factors.

Abstract

We assessed joint associations of cardiorespiratory fitness and diabetes, cardiovascular disease (CVD), or both with all-cause mortality. High-fitness eliminated mortality risk in diabetes (P<0.001) and halved risk of death in diabetes/CVD (P<0.001). Fitness was a potent effect modifier in the association of diabetes and CVD to mortality.

Abstract

A graded nonlinear relationship exists between fitness and mortality with the most remarkable difference in mortality rates observed between the least-fit (first, Q1) and the next-least-fit (second, Q2) quintile of fitness. The purpose of this study was to compare clinical characteristics, exercise test responses, and physical activity patterns in Q1 versus Q2 in apparently healthy individuals.A total of 4384 subjects referred for clinical treadmill testing from 1986 to 2006 were followed for a mean +/- SD period of 8.7 +/- 5.3 yr. All subjects had normal exercise ECG responses and no history of cardiovascular disease. Subjects were classified into quintiles of exercise capacity measured in METs. Clinical characteristics, physical activity patterns, and treadmill test results were compared between the first two quintiles (Q1: METs <5.9 (n = 693); Q2: METs 6.0-7.9 (n = 842)).Small differences in age (64 +/- 11 vs 60 +/- 10 yr, P < 0.001), use of antihypertensive medications, prevalence of diabetes (21% vs 16%, P = 0.02), and dyslipidemia (43% vs 49%, P = 0.04) were observed between Q1 and Q2. When the Cox proportional hazards model was adjusted for age and other clinical characteristics, the relative risk of mortality remained almost two times greater in Q1 versus Q2 (cardiovascular mortality: HR: 4.01 vs 2.01, P < 0.001; reference group: fittest subjects (Q5)). In a subset of 802 subjects, recent recreational physical activity was significantly lower in Q1 versus Q2.Reduced physical activity patterns rather than differences in clinical characteristics contribute to the striking difference in mortality rates between the least-fit and the next-least-fit quintile of fitness in healthy individuals.

Abstract

Maximal oxygen pulse (O(2) pulse) mirrors the stroke volume response to exercise, and should therefore be a strong predictor of mortality. Limited and conflicting data are, however, available on this issue.Nine hundred forty-eight participants, classified as those with cardiopulmonary disease (CPD) and those without (non-CPD), underwent cardiopulmonary exercise testing (CPX) for clinical reasons between 1993 and 2003. The ability of maximal O(2) pulse and maximal oxygen uptake (peak VO(2)) to predict mortality was investigated using proportional hazards and Akaike information criterion analyses. All-cause mortality was the endpoint.Over a mean follow-up of 6.3+/-3.2 years, there were 126 deaths. Maximal O(2) pulse, expressed in either absolute or relative to age-predicted terms, and peak VO(2) were significant and independent predictors of mortality in those with and without CPD (P<0.04). Akaike information criterion analysis revealed that the model including both maximal O(2) pulse and peak VO(2) had the highest accuracy for predicting mortality. The optimal cut-points for O(2) pulse and peak VO(2) (<12; > or =12 ml/beat and <16; > or =16 ml/(kg.min) respectively) were established by the area under the receiver-operating-characteristic curve. The relative risks of mortality were 3.4 and 2.2 (CPD and non-CPD, respectively) among participants with both maximal O(2) pulse and peak VO(2) responses below these cut-points compared with participants with both responses above these cut-points.These results indicate that maximal O(2) pulse is a significant predictor of mortality in patients with and without CPD. The addition of absolute and relative O(2) pulse data provides complementary information for risk-stratifying heterogeneous participants referred for CPX and should be routinely included in the CPX report.

Abstract

Low body mass index (BMI) and low cardiorespiratory fitness (CRF) are independently associated with increased mortality in the elderly. However, interactions among BMI, CRF, and mortality in older persons have not been adequately explored.Hazard ratios (HRs) were calculated for predetermined strata of BMI and CRF. Independent and joint associations of CRF, BMI, and all-cause mortality were assessed by Cox proportional hazards analyses in a prospective cohort of 981 healthy men aged at least 65 years (mean age [+/-SD], 71 [+/-5] years; range, 65-88 years) referred for exercise testing during 1987-2003.During a mean follow-up of 6.9 +/- 4.4 years, a total of 208 patients died. Multivariate relative risks (95% confidence interval [CI]) of mortality across BMI groups of <20.0, 20.0-25.0, 25.0-29.9, 30.0-34.9, and > or =35.0 were 2.51 (1.26-4.98), 1.0 (reference), 0.66 (0.48-0.90), 0.50 (0.31-0.78), and 0.44 (0.20-0.97), respectively, and across CRF groups of <5.0, 5.0-8.0, and >8.0 metabolic equivalents were 1.0 (reference), 0.56 (0.40-0.78), and 0.39 (0.26-0.58), respectively. In a separate analysis of within-strata CRF according to BMI grouping, the lowest mortality risk was observed in obese men with high fitness (HR [95% CI] 0.26 [0.10-0.69]; p = .007).In this cohort of elderly male veterans, we observed independent and joint inverse relations of BMI and CRF to mortality. This warrants further investigation of fitness, fatness, and mortality interactions in older persons.

Abstract

Electrocardiogram (ECG) scores have been demonstrated to predict CV mortality but they are rarely utilized clinically.Develop a simple score consisting of adding classical ECG abnormalities to make the ECG a more convenient prognostic tool.Resting ECGs of 29,320 outpatient male veterans from the Palo Alto Veteran Affairs Healthcare System (PAVHS) collected between 1987 and 2000 were computer analyzed with an average follow-up of 7.5 y. Twelve classic ECG abnormalities were chosen on the basis of prevalence and corresponding relative risks, including left and right bundle branch block, diagnostic Q waves, intraventricular conduction defect, atrial fibrillation, left atrial abnormality, left and right axis deviation, left and right ventricular hypertrophy, ST depression, and abnormal QTc interval. A simple score derived from the summation of these criteria was then entered into an age and heart rate adjusted Cox analysis.There was a progressive increase in risk of death as the number of ECG abnormalities increased. The relative risks for 1, 2, 3, 4, and 5 ECG abnormalities were 1.8 (CI 1.6-2.0), 2.4 (CI 2.2-2.7), 3.6 (CI 3.2-4.1), 4.5 (CI 3.8-5.4), and 6.0 (CI 4.7-7.8) respectively (p < 0.001). The age-adjusted hazard ratio for CV mortality was 6.0 when there were five or more ECG abnormalities present.Summing the number of classical ECG abnormalities provides a powerful predictor of CV mortality independent of age, standard risk factors, and clinical status.

Abstract

Premature ventricular complexes (PVCs) during exercise are associated with adverse prognosis, particularly in patients with intermediate treadmill test findings. Statin use reduces the incidence of resting ventricular arrhythmias in patients with coronary artery disease; however, the relationship between statin use and exercise-induced ventricular arrhythmias has not been investigated.We evaluated the association between statin use and PVCs in 1,847 heart-failure-free patients (mean age 58, 95% male) undergoing clinical exercise treadmill testing between 1997 and 2004 in the VA Palo Alto Health Care System. PVCs were quantified in beats per minute and frequent PVCs were defined as PVC rates greater than the median value (0.43 and 0.60 PVCs per minute for exercise and recovery, respectively). Propensity-adjusted logistic regression was used to evaluate the odds of developing PVCs during exercise and recovery periods associated with statin use. There were 431 subjects who developed frequent PVCs during exercise and 284 subjects had frequent recovery PVCs. After propensity score adjustment, subjects treated with statins (n = 145) had 42% lower odds of developing frequent PVCs during exercise (odds ratio [OR] 0.58, 95% confidence interval [CI] 0.37-0.93) and 44% lower odds of developing frequent PVCs during recovery (OR 0.56, 95% CI 0.30-0.94). These effects were not modified by age, prior coronary disease, hypercholesterolemia, exercise-induced angina, or exercise capacity.Statin use was associated with reduced odds of frequent PVCs during and after clinical exercise testing in a manner independent of associations with coronary disease or ischemia in our study population.

Abstract

The resting 12-lead electrocardiogram (ECG) remains the most commonly used test in evaluating patients with suspected cardiovascular disease. Prognostic values of individual findings on the ECG have been reported but may be of limited use.The characteristics of 45,855 ECGs ordered by physician's discretion were first recorded and analyzed using a computerized system. Ninety percent of these ECGs were used to train an artifical neural network (ANN) to predict cardiovascular mortality (CVM) based on 132 ECG and four demographic characteristics. The ANN generated a Resting ECG Neural Network (RENN) score that was then tested in the remaining ECGs. The RENN score was finally assessed in a cohort of 2189 patients who underwent exercise treadmill testing and were followed for CVM.The RENN score was able to better predict CVM compared to individual ECG markers or a traditional Cox regression model in the testing cohort. Over a mean of 8.6 years, there were 156 cardiovascular deaths in the treadmill cohort. Among the patients who were classified as intermediate risk by Duke Treadmill Scoring (DTS), the third tertile of the RENN score demonstrated an adjusted Cox hazard ratio of 5.4 (95% CI 2.0-15.2) compared to the first RENN tertile. The 10-year CVM was 2.8%, 8.6% and 22% in the first, second and third RENN tertiles, respectively.An ANN that uses the resting ECG and demographic variables to predict CVM was created. The RENN score can further risk stratify patients deemed at moderate risk on exercise treadmill testing.

Abstract

The Duke Treadmill Score (DTS) is an established clinical tool for risk stratification. Our aim was to determine if other variables could improve the prognostic power of the DTS and if so, to modify the DTS nomogram. From a total of 1,959 patients referred for exercise testing at the Palo Alto VA Medical Center from 1997 to 2006 (a mean follow-up of 5.4 years), we studied 1,759 male veterans (age 57 +/- 12 years) free of heart failure. Double product (DP) was calculated by multiplying systolic blood pressure and heart rate; variables and their products were subtracted to obtain the differences between at rest and maximal exercise (reserve) and recovery. Of all the hemodynamic measurements, DP reserve was the strongest predictor of cardiovascular death (CVD) (Wald Z-score -3.84, p <0.001) after adjustment for potential confounders. When the components of DTS were entered in the Cox hazard model with DP reserve and age, only DP reserve and age were chosen (p <0.00001). Using the Cox coefficients, a score calculated by [age - DTS - 3 x (DP reserve/1,000)] yielded an area under the curve of 0.84 compared with 0.76 for the DTS. Using this equation, a nomogram was constructed by adding age and DP reserve to the original DTS nomogram improving estimation of annual CVD. In conclusion, we propose an age and DP reserve-adjusted DTS nomogram that improves the prognostic estimates of average annual CVD over the DTS alone.

Abstract

Discriminatory capabilities of a measurement technique can be assessed by a receiver operating characteristic (ROC) curve analysis (specifically, area under the curve [AUC]) and predictive modeling (predictive accuracy and positive predictive value). Theoretically, predictive accuracy is dependent on disease prevalence while AUC assessments are not.To compare the effect of changes in disease prevalence on ROC AUC analysis and predictive modeling.For this comparison, a data set with 72 individuals with coronary artery disease (CAD) and 1,857 individuals without CAD was used. A validated CAD score with a demonstrated AUC of 0.80 was applied. Disease prevalence within the study sample was altered by randomly removing non-CAD patients from the original sample. Predictive accuracy and positive predictive value of the CAD score were calculated using 2 x 2 contingency tables. Three threshold values of the CAD score were applied centering on a value for which sensitivity and specificity were equal.For a chosen CAD score threshold value (eg, 60), sensitivity (0.74), specificity (0.75), and AUC (0.81) did not change significantly while positive predictive value increased (10%-70%) as disease prevalence increased from 4% to 44%. Changes in predictive accuracy were dependent on the selected test threshold value. Predictive accuracy increased (54%-68%), did not change (74%-75%), or decreased (88%-70%) with the same increase in disease prevalence for threshold values of 50, 60, and 70, respectively.The ROC AUC and predictive accuracy are stable diagnostic characteristics, whereas positive predictive value is greatly influenced by disease prevalence.

Abstract

Although the prognostic power of exercise capacity has been demonstrated, the relative prognostic potential of other hemodynamic responses has not been thoroughly investigated. We aimed to assess the prognostic power of double product (DP) parameters in patients referred for standard exercise testing.A retrospective cohort study.Analyses were performed on 1959 patients referred for exercise testing at the Palo Alto Veterans Affairs Medical Center from 1997 to 2006. After removal of female and heart failure patients, 1759 male veterans (mean age 57+/-12 years) remained. DP was calculated by multiplying systolic blood pressure (SBP) and heart rate (HR); variables and their products were subtracted to obtain the differences between rest and maximal exercise (reserve), and recovery.Multivariable Cox survival analysis was performed for 157 all-cause and 53 cardiovascular deaths during a mean follow-up of 5.4+/-2.1 years. Although most of the hemodynamic variables were individually significant in Cox survival analysis, when age, DP reserve, exercise capacity (in metabolic equivalents), and HR recovery were entered together, only age and DP reserve were chosen. Of all hemodynamic measurements considered, DP reserve was the strongest predictor of cardiovascular prognosis after adjustment for age (Wald Z-score,-5.12; P<0.0001) and when considering other potential confounders such as age, beta-blocker use, and the Duke treadmill Score (Wald Z-score,-3.84; P<0.0001).In this study population, DP reserve had greater prognostic power than metabolic equivalents, maximal HR or systolic blood pressure, or HR recovery.

Abstract

Although blood pressure (BP) is measured routinely during exercise testing, its clinical significance is not fully understood or appreciated. As the number of studies has increased, conflicting data have emerged, partly due to differences in methodologies, populations studied, testing procedures, and definitions used for an abnormal BP response. This article attempts to review the literature studying the physiology and pathophysiology of the BP response to exercise testing and summarize the evidence for its diagnostic and prognostic applications.

Abstract

Reassertion of vagal tone after exercise is an important component in mediating heart rate recovery (HRR), and both vagal tone and HRR have been associated with mortality. HRR is strongly related to the increase in HR from resting to peak exercise. We hypothesized that a score normalized for HR increase would better isolate the vagal influences in recovery from the sympathetic influences supporting maximal exercise.HRR data from 1959 veterans were analyzed. During a mean follow-up of 5.3 years, 187 (9.5%) subjects died-70 (37%) due to cardiovascular (CV) causes. A method was developed to compare HRR curve shapes normalized for differences in HR increase. Differences in the slopes of the normalized curves over the range 50-70 s were observed between the survivors and nonsurvivors, and a prognostic measurement, HRRS50-70, was developed. The incremental increases in predictive power and discriminative accuracy provided by Duke Treadmill Score (DTS), clinical parameters, HR increase, recovery variables, and HRRS50-70 were assessed.In the age-adjusted Cox analysis, the only significant exercise indices associated with CV mortality were HR increase (P < 0.0001), HRRS50-70 (P = 0.01), and DTS (P < 0.001). The increased risk for patients in the lowest tertile for all three indices, relative to those with normal scores, was 22 (95% CI, 7.9-63; P < 0.0001).HRRS50-70 is independent of and complementary to HR increase and DTS. Patients with abnormal HRRS50-70 and abnormal DTS and/or HR increase are at substantially increased risk of CV mortality.

Abstract

The Duke Treadmill Score (DTS) is an established clinical tool for risk stratification of patients referred for exercise testing, but it does not consider age. We aimed to determine if age could improve the prognostic power of the DTS and if so, to modify the DTS nomogram to include age.Of 1,959 patients referred for exercise testing from 1997 to 2006, 1,759 male veterans (age range 23-86 years) remained after exclusion of female and patients with heart failure. Cardiovascular mortality was the main outcome considered.Cox survival analysis was performed entering age and the DTS; both were significant (P

Abstract

Extensive evidence is available that cardiovascular structure and function, along with other biological properties that span the range of organism size and speciation, scale with body size. Although appreciation of such factors is commonplace in pediatrics, cardiovascular measurements in the adult population, with similarly wide variation in body size, are rarely corrected for body size. In this review, we describe the critical role of body size measurements in cardiovascular medicine. Using examples, we illustrate the confounding effects of body size. Current cardiovascular scaling practices are reviewed, as are limitations and alternative relationships between body and cardiovascular dimensions. The experimental evidence, theoretical basis, and clinical application of scaling of various functional parameters are presented. Appropriately scaled parameters aid diagnostic and therapeutic decision making in specific disease states such as hypertrophic cardiomyopathy and congestive heart failure. Large-scale studies in clinical populations are needed to define normative relationships for this purpose. Lack of appropriate consideration of body size in the evaluation of cardiovascular structure and function may adversely affect recognition and treatment of cardiovascular disease states in the adult patient.

Abstract

Since there is an uncertainty regarding which of the 12 leads provides the most information, we investigated the association between repolarization phenomenon in all of the 12 leads and cardiovascular (CV) mortality.Retrospective cohort study was performed at Palo Alto Veterans Affairs Medical Center, Palo Alto, California, which included 24,270 consecutive male veterans with ECGs obtained for clinical reasons from 1987 to 2000. Analysis of computerized 12-lead resting ECGs was performed of all subjects excluding inpatients, patients with atrial fibrillation, WPW, QRS duration > 120 ms, and paced rhythms. Average follow-up was 7.5 years during which time there were 1859 CV deaths.While ST segment measurements in aVR were univariately predictive of CV death, T wave amplitude superseded them in multivariate survival analysis. In addition, T wave amplitude in aVR outperformed repolarization measurements in all other leads as well as other ECG criteria (Q waves, damage scores, LVH) for predicting CV mortality. As T wave amplitude became less negative in aVR, there was a progressive increase in relative risk (RR). When the T waves in aVR had a positive deflection (i.e., upward pointing) the RR for CV death was 5.0.T wave amplitude in lead aVR is a powerful prognostic marker for estimating risk of CV death. Upward pointing T waves (a simple visual criterion) was prevalent (7.3% of a clinical population) and was associated with an annual CV mortality of 3.4% and a risk of five times.

Abstract

Our aim was to investigate whether exercise-induced increase in systolic blood pressure (BP) measured during exercise stress testing (EST) adds prognostic information to cardiovascular (CV) mortality. EST is ideally suited to evaluate the prognostic power of systolic BP; it not only measures systolic BP response to exercise but also provides information about exercise capacity and other EST variables, which may affect the peak systolic BP. The study population consisted of 6,145 consecutive patients who underwent symptom-limited EST. Using the median value of change in systolic BP from baseline, patients were grouped according to exercise-induced increases in systolic BPor=44 mm Hg (group B, n=3,083). Multivariate analysis was used to adjust for baseline differences between the 2 groups with CV mortality as the end point for follow-up. Six thousand one hundred forty-five men underwent EST with a mean follow-up of 6.6 years. During follow-up, 676 patients died of CV causes with an average annual CV mortality of 1.6%. CV mortality was significantly higher in group A than in group B (13.7% vs 8.2%, p<0.001). After adjusting for baseline differences in the 2 groups using multivariate analysis, an increase in systolic BP of or=44 mm Hg during EST was associated with a 23% improvement in survival over a mean follow-up of >6 years.

Abstract

To demonstrate the relation of exercise capacity and BMI to mortality in a population of male veterans with type 2 diabetes.After excluding two underweight patients (BMI <18.5 kg/m2), the study population comprised 831 consecutive patients with type 2 diabetes (mean age 61 +/- 9 years) referred for exercise testing for clinical reasons between 1995 and 2006. Exercise capacity was determined from a maximal exercise test and measured in metabolic equivalents (METs). Patients were classified both according to BMI category (18.5-24.9, 25.0-29.9, and > or =30 kg/m2) and by exercise capacity (<5.0 or > or =5.0 maximal METs). The association among exercise capacity, BMI, other clinical variables, and all-cause mortality was assessed by Cox proportional hazards. Study participants were followed for mortality up to 30 June 2006.During a mean follow-up of 4.8 +/- 3.0 years, 112 patients died, for an average annual mortality rate of 2.2%. Each 1-MET increase in exercise capacity conferred a 10% survival benefit (hazard ratio 0.90 [95% CI 0.82-0.98]; P = 0.01), but BMI was not significantly associated with mortality. After adjustment for age, ethnicity, examination year, BMI, presence of cardiovascular disease (CVD), and CVD risk factors, diabetic patients achieving <5 maximal METs were 70% more likely to die (1.70 [1.13-2.54]) than those achieving > or =5 maximal METs.There was a strong inverse association between exercise capacity and mortality in this cohort of men with documented diabetes, and this relationship was independent of BMI.

Abstract

The paradox of obesity in patients with heart failure (HF) also has been observed in non-HF veteran patients. Veterans had to have met military fitness requirements at the time of their enlistment. Therefore, we assessed the relation of body mass index (BMI) to mortality in a clinical cohort of non-HF veterans, adjusting for fitness.After excluding HF patients (n=580), the study population comprised 6876 consecutive patients (mean age 58 [+/-11] years) referred for exercise testing. Patients were classified by BMI category: normal weight (BMI 18.5-24.9 kg/m2), overweight (BMI 25.0-29.9 kg/m2), or obese (BMI > or =30.0 kg/m2). The association between BMI, fitness, other clinical variables, and all-cause mortality was assessed by Cox proportional hazards analysis.During a mean (+/-SD) follow-up of 7.5+/-4.5 years, a total of 1571 (23%) patients died. In a multivariate analysis including clinical, risk factor, and exercise test data, higher BMI was associated with better survival. Expressing the data by BMI category, obese patients were 22% less likely to die (relative risk [RR]=0.78, 95% confidence interval [CI], 0.69-0.90, P

Abstract

The prevalence and prognostic values of electrocardiogram (ECG) abnormalities in Hispanics have not been compared to other ethnicities in a large population. Despite a worse cardiovascular risk profile, the prevalence of cardiovascular disease is lower in Hispanics compared to non-Hispanics.We hypothesized that ECG abnormalities were less common in Hispanics and were not as strongly associated with cardiovascular mortality.45,563 ECGs ordered for usual clinical indications in a Veteran's hospital were available for analysis. 1,392 patients who died within one week of the ECG were excluded. Demographic characteristics were recorded and the population was followed for an average of 7.5 years using the California Death Index. The presence of baseline ECG characteristics were recorded and analyzed using the GE/Marquette computerized ECG system. Age, sex and heart rate adjusted Cox hazard ratio analyses were performed.Being Hispanic was associated with lower cardiovascular death, with a hazard ratio (HR) of 0.76 (95% CI 0.65-0.89). Findings such as atrial fibrillation, presence of Q-waves, left ventricular hypertrophy (LVH), upright T-waves in aortic valve replacement (aVR) and cardiac Infarction Injury Scores > 6 were significantly less prevalent in Hispanics than in non-Hispanics. These findings were similarly associated with increased cardiovascular mortality in both groups, each with a HR of approximately 2.The lower prevalence of ECG characteristics associated with coronary heart disease, atrial fibrillation and left ventricular hypertrophy support prior observations that cardiovascular disease is less prevalent in the Hispanic population. These findings, however, are similarly associated with increased mortality compared to non-Hispanics.

Abstract

Both an impaired capacity to increase heart rate during exercise testing (chronotropic incompetence), and a slowed rate of recovery following exercise (heart rate recovery) have been shown to be associated with all-cause mortality. It is, however, unknown which of these responses more powerfully predicts risk, and few data are available on their association with cardiovascular mortality or how they are influenced by beta-blockade.Routine symptom-limited exercise treadmill tests performed on 1910 male veterans at the Palo Alto Veterans Affairs Medical Center from 1992 to 2002 were analyzed. Heart rate was determined each minute during exercise and recovery. Chronotropic incompetence was defined as the inability to achieve > or =80% of heart rate reserve, using a population-specific equation for age-predicted maximal heart rate. An abnormal heart rate recovery was considered to be a decrease of <22 beats/min at 2 min in recovery. Cox proportional hazards analyses including pretest clinical data, chronotropic incompetence, heart rate recovery, the Duke Treadmill Score (abnormal defined as <4), and other exercise test responses were performed to determine their association with cardiovascular mortality.Over a mean follow-up of 5.1+/-2.1 years, there were 70 deaths from cardiovascular causes. Both abnormal heart rate recovery and chronotropic incompetence were associated with higher cardiovascular mortality, a lower exercise capacity, and more frequent occurrence of angina during exercise. Both heart rate recovery and chronotropic incompetence were stronger predictors of risk than pretest clinical data and traditional risk markers. Multivariately, chronotropic incompetence was similar to the Duke Treadmill Score for predicting cardiovascular mortality, and was a stronger predictor than heart rate recovery [hazard ratios 3.0 (95% confidence interval 1.9-4.9), 2.8 (95% confidence interval 1.7-4.8), and 2.0 (95% confidence interval 1.1-3.5) for abnormal Duke Treadmill Score, chronotropic incompetence, and abnormal heart rate recovery, respectively]. Having both chronotropic incompetence and abnormal heart rate recovery strongly predicted cardiovascular death, resulting in a relative risk of 4.2 compared with both responses being normal. Beta-blockade had minimal impact on the prognostic power of chronotropic incompetence and heart rate recovery.Both chronotropic incompetence and heart rate recovery predict cardiovascular mortality in patients referred for exercise testing for clinical reasons. Chronotropic incompetence was a stronger predictor of cardiovascular mortality than heart rate recovery, but risk was most powerfully stratified by these two responses together. The simple application of heart rate provides powerful risk stratification for cardiovascular mortality from the exercise test, and should be routinely included in the test report.

Abstract

We sought to evaluate the prognostic significance of premature ventricular contractions (PVCs) on a routine electrocardiogram (ECG) and to evaluate the relationship between heart rate and PVCs.Computerized 12-lead ECGs of 45,402 veterans were analyzed. Vital status was available through the California Health Department Service.There were 1731 patients with PVCs (3.8%). Compared to patients without PVCs, those with PVCs had significantly higher all-cause (39% vs 22%, P < 0.001) and cardiovascular mortality (20% vs 8%, P < 0.001). PVCs remain a significant predictor even after adjustment for age and other ECG abnormalities. The presence of multiple PVCs or complex morphologies did not add significant additional prognostic information. Those patients with PVCs had a significantly higher heart rate than those without PVCs (mean +/- SD: 78.6 +/- 15 vs 73.5 +/- 16 bpm, P < 0.001). When patients were divided into groups by heart rate (<60, 60-79, 80-99 and >100 bpm) and by the presence or absence of PVCs, mortality increased progressively with heart rate and doubled with the presence of PVCs. Using regression analysis, heart rate was demonstrated to be an independent and significant predictor of PVCs.PVCs on a resting ECG are a significant and independent predictor of all-cause and cardiovascular mortality. Increased heart rate predicts mortality in patients with and without PVCs and the combination dramatically increases mortality. These findings together with the demonstrated independent association of heart rate with PVCs suggest that a hyperadrenergic state is present in patients with PVCs and that it likely contributes to their adverse prognosis.

Abstract

Although the prognostic power of heart rate variability (HRV) at rest has been demonstrated, the prognostic potential of exercise-induced HRV has not been investigated. We aimed to evaluate the prognostic power of exercise-induced HRV during and after standard exercise testing.Time- and frequency-domain HRV analysis was performed on R-R interval data taken from 1335 subjects (95% male, mean age 58 years) during the first and last 2 minutes of exercise treadmill testing and the first 2 minutes of recovery. Cox survival analysis was performed for the 53 cardiovascular and 133 all-cause mortality end points that accrued during the 5.0-year mean follow-up.After adjusting for potential confounders, greater root mean square successive difference in R-R interval during peak exercise and recovery, greater high-frequency (HF) power and percentage of HF power, lower percentage of low-frequency power, and lower ratio of low frequency to HF during recovery were significantly associated with increased risks for all-cause and cardiovascular death. Of all time-domain variables considered, the log of the root mean square successive difference during recovery was the strongest predictor of cardiovascular mortality (adjusted hazard ratio 5.0, 95% CI 1.5-17.0 for the top quintile compared with the lowest quintile). Log HF power during recovery was the strongest predictor of cardiovascular mortality in the frequency domain (adjusted hazard ratio 5.9, 95% CI 1.3-25.8 for the top quintile compared with the lowest quintile).Exercise-induced HRV variables during and after clinical exercise testing strongly predict both cardiovascular and all-cause mortality independent of clinical factors and exercise responses in our study population.

Abstract

The initial response of heart rate to dynamic exercise has been proposed as having prognostic value in limited studies that have used modalities other than the treadmill. Our aim was to evaluate the prognostic value of early heart rate parameters in patients referred for routine clinical treadmill testing.The heart rate rise at the onset of exercise was measured in 1959 patients referred for clinical treadmill testing at the Palo Alto (Calif) Veterans Affairs Medical Center from 1997 to 2004. Multivariable Cox survival analysis was performed for 197 all-cause and 74 cardiovascular deaths that accrued during a mean follow-up of 5.4+/-2.1 years. Decreased heart rate changes at all initial relative exercise workloads were associated with significantly increased all-cause mortality. The heart rate rise at one-third total exercise capacity, however, was the only early heart rate variable that significantly predicted both all-cause and cardiovascular risk after adjustment for confounders. Failing to reach 1 SD in the heart rate rise at one-third total exercise capacity was associated with a 28% increased all-cause mortality rate (hazard ratio, 0.72; 95% CI, 0.61 to 0.85; P<0.001) and a 35% cardiovascular mortality rate (hazard ratio, 0.65; 95% CI, 0.49 to 0.86; P=0.003). Of all heart rate measurements considered (initial and recovery), the heart rate increase at peak exercise was the most powerful predictor of cardiovascular prognosis after adjustment for potential confounders. The Duke treadmill score, however, was superior to all heart rate measurements in the prediction of cardiovascular mortality.In the present study population, a rapid initial heart rate rise was associated with improved survival, but the heart rate increase at peak exercise and other conventional measurements such as exercise capacity and the Duke treadmill score were more powerful predictors of prognosis.

Abstract

Heart rate recovery (HRR) during exercise testing is an independent predictor of prognosis. The relative predictive power of computational analysis of HRR as a function of resting and maximum heart rate (HR) compared with direct measurement of the drop in HR has not been determined.We aimed to improve on the prognostic value of HRR by the use of mathematical representations of HRR kinetics.In all, 2,193 patients who underwent exercise testing, coronary angiography, and clinical evaluation were followed up for 10.2 +/- 3.6 years. Mathematical functions were used to model HRR as a function of resting (HR(Rest)), maximum HR (HR(Peak)) and time (t): (a) HRR= HR(Rest) + (HR(peak) - HR(Rest)) X e(-kt) and (b) HRR= HR(Rest) + (HR(peak) - HR(Rest)) e(-kt2)Equation (b) provided the best fit of the recovery HR curve. An abnormal HRR at 2 min was a better predictor of mortality than HRR at 1, 3, or 5 min. At 2 min, HRR also predicted mortality better than computational models of HRR, relating HRR as a function of maximum and resting HRs. After adjusting for univariately significant predictors of mortality, HRR, age, exercise capacity, and maximum HR were chosen in order as the best predictors of mortality.Even though the computational models of HRR and the determination of HRR at different time intervals were significant predictors of mortality, the simple discrete measure of HRR at 2 min was the best predictor of mortality. At 2 min, HRR outperformed age, METs, and maximum exercise HR in predicting all-cause mortality.

Abstract

A wide variety of instruments have been used to assess the functional capabilities and health status of patients with chronic heart failure (HF), but it is not known how well these tests are correlated with one another, nor which one has the best association with measured exercise capacity.Forty-one patients with HF were assessed with commonly used functional, health status, and quality of life measures, including maximal cardiopulmonary exercise testing, the Duke Activity Status Index (DASI), the Veterans Specific Activity Questionnaire (VSAQ), the Kansas City Cardiomyopathy Questionnaire (KCCQ), and 6-minute walk distance. Pretest clinical variables, including age, resting pulmonary function tests (forced expiratory volume in 1 s and forced vital capacity), and ejection fraction (EF) were also considered. The association between performance on these functional tools, clinical variables, and exercise test responses including peak VO2 and the VO2 at the ventilatory threshold, was determined. Peak oxygen uptake (VO2) was significantly related to VO2 at the ventilatory threshold (r = 0.76, P < .001) and estimated METs from treadmill speed and grade (r = 0.72, P < .001), but had only a modest association with 6-minute walk performance (r = 0.49, P < .01). The functional questionnaires had modest associations with peak VO2 (r = 0.37, P < .05 and r = 0.26, NS for the VSAQ and DASI, respectively). Of the components of the KCCQ, peak VO2 was significantly related only to quality of life score (r = 0.46, P < .05). Six-minute walk performance was significantly related to KCCQ physical limitation (r = 0.53, P < .01) and clinical summary (r = 0.44, P < .05) scores. Among pretest variables, only age and EF were significantly related to peak VO2 (r = -0.58, and 0.46, respectively, P < .01). Multivariately, age and KCCQ quality of life score were the only significant predictors of peak VO2, accounting for 72% of the variance in peak VO2.Commonly used functional measures, symptom tools, and quality of life assessments for patients with HF are poorly correlated with one another and are only modestly associated with exercise test responses. These findings suggest that exercise test responses, non-exercise test estimates of physical function, and quality of life indices reflect different facets of health status in HF and one should not be considered a surrogate for another.

Abstract

The purpose of this study was to investigate the phenomenon of left ventricular (LV) dysfunction after ultraendurance exercise.Subclinical LV dysfunction in response to endurance exercise up to 24 h duration has been described, but its mechanism remains elusive.We tested 86 athletes before and after the Adrenalin Rush Adventure Race using echocardiography, impedance cardiography, and plasma immunoassay.At baseline, athletes demonstrated physiology characteristic of extreme endurance training. After 90 to 120 h of almost-continuous exercise, LV systolic and diastolic function declined (fractional shortening before the race, 39.6 +/- 0.65%; after, 32.2 +/- 0.84%, p < 0.001; mitral inflow E-wave deceleration time before the race, 133 +/- 5 ms; after, 160 +/- 5 ms, n = 48, p < 0.001) without change in loading conditions as defined by LV end-diastolic dimension and total peripheral resistance estimated by thoracic impedance. There was a compensatory increase in heart rate (before, 55 +/- 1.3 beats/min; after, 59 +/- 1.5 beats/min, p = 0.05), which left cardiac output unchanged, as well as significant-but-subclinical increases in brain natriuretic peptide and troponin I. In addition, we found that athletes who were homozygous for the intron-16 insertion polymorphism of the angiotensin-converting enzyme (ACE) gene exhibited a significantly greater decrease in fractional shortening than athletes who were homozygous for the deletion allele. Heterozygotes showed an intermediate phenotype. In addition, the deletion group manifest an enhanced sympathovagal balance after the race, as evidenced by greater power in the low-frequency component of blood pressure variability.The ACE genotype predicts the extent of reversible subclinical LV dysfunction after prolonged exercise and is associated with a differential postactivity augmentation of sympathetic nervous system function that may explain it.

Abstract

Cross-sectional analysis of a convenience sample of locally recruited participants, including both patients and volunteers.To determine whether there is an association between plasma homocysteine and hypertension in persons with spinal cord injury (SCI).Spinal Cord Injury Service of the Veterans Affairs Palo Alto Medical Center (California, United States of America).The incidence of hypertension, dyslipidemia, insulin resistance, and the presence of metabolic syndrome were determined in 168 individuals with SCI (mean age 50.2 +/- 12.8 years). Fasting lipids, insulin, glucose, plasma homocysteine, and anthropometric data was gathered for each subject.Blood pressure values (P < 0.001) and mean arterial pressure (P < 0.05) increased with higher plasma homocysteine levels. Homocysteine values were also significantly greater among individuals with hypertension compared with those who were normotensive or prehypertensive (P < 0.0001). There was an inverse relationship between plasma homocysteine levels and glomerular filtration rate and effective renal plasma flow (P < 0.05).Plasma homocysteine levels are elevated in persons with SCI who have hypertension and inversely related to renal function, which suggests that renal dysfunction may be a link between homocysteine and hypertension in persons with SCI.Funded by the VA Rehabilitation Research and Development Service, Merit Review Grant #B2549R.

Abstract

Although QRS duration is known to be a predictor of mortality in patients with left ventricular dysfunction, our purpose was to evaluate the prognostic power of computer-measured QRS duration in a general medical population.Analyses were performed on the first electrocardiogram digitally recorded on 46,933 consecutive patients at the Palo Alto Veterans Affairs Medical Center between 1987 and 2000. Patients with electrocardiograms exhibiting Wolff-Parkinson-White were excluded (n = 44), and those with bundle branch block or electronic pacing were considered separately, leaving 44,280 patients for analysis (mean age 56 +/- 15 years; 90% were males). There were 3659 (8.3%) cardiovascular deaths (mean follow-up of 6.0 +/- 3.8 years).A survival plot showed significant separation according to a QRS duration score. After adjustment in the Cox model for age, gender, and heart rate, the QRS duration score was a strong independent predictor of cardiovascular mortality. For every 10-ms increase in QRS duration, there was an 18% increase in cardiovascular risk. The results were similar in patients with an abnormal electrocardiogram, a bundle branch block, and a paced rhythm.Quantitative QRS duration was a significant and independent predictor of cardiovascular mortality in a general medical population.

Abstract

A self-administered symptom questionnaire developed at our institution (Veterans Specific Activity Questionnaire [VSAQ]) is routinely used to estimate a patient's exercise capacity to individualize the exercise test in accordance with current guidelines. This study was performed to evaluate the association of the VSAQ with all-cause mortality.The VSAQ was administered to 1185 consecutive male patients (mean age 58 +/- 12 years) referred for exercise testing for clinical reasons. The VSAQ is designed to determine which specific daily activities are associated with cardiovascular symptoms (fatigue, chest pain, or shortness of breath) to provide an estimate of exercise tolerance (in metabolic equivalents [METs]) before exercise testing. Patients were classified into 1 of 3 groups according to VSAQ score: <5 METs, 5 to 8 METs, and >8 METs. The association between exercise capacity estimated by the VSAQ, other clinical and exercise test variables, and all-cause mortality was assessed by Cox proportional hazards. The mean follow-up period was 4.5 +/- 2.9 years.There were a total of 132 deaths during the follow-up period, resulting in an average annual mortality of 2.7%. In a multivariate analysis including clinical risk factors and exercise test variables, age-adjusted predictors of mortality, in rank order, were the VSAQ score in METs, history of chronic heart failure, history of smoking, and diabetes (for VSAQ: hazard ratio [HR] 0.90, 95% CI 0.83-0.98; for chronic heart failure: HR 2.67; 95% CI 1.51-4.72; for smoking: HR 1.74, 95% CI 1.18-2.57; and for diabetes: HR 1.84, 95% CI 1.15-2.95). Expressed in tertiles, age-adjusted relative risks for the VSAQ were 1.0, 0.54, and 0.22 (P for trend

Abstract

There is considerable recent evidence that parameters thought to reflect the complex interaction between the autonomic nervous system and the cardiovascular system during exercise testing can provide significant prognostic information. Specific variables of great importance include heart rate (HR) response to exercise (reserve), HR recovery after exercise, and multiple components of HR variability both at rest and with exercise. Poor HR response to exercise has been strongly associated with sudden cardiac death and HR recovery from a standard exercise test has been shown to be predictive of mortality. In addition, there are limited studies evaluating the components of HR variability at rest and during exercise and their prognostic significance. Research continues seeking to refine these exercise measurements and further define their prognostic value. Future findings should augment the power of the exercise test in risk-stratifying cardiovascular patients.

Abstract

The ability to better predict outcome with exercise testing in patients with heart failure (HF) and left ventricular systolic dysfunction (LVSD) may prove extremely valuable in determining which patients are at increased risk. This study evaluated the ability of heart rate recovery (HRR) to predict outcome in patients with HF and validate previous findings in LVSD.HRR was measured at 1-, 2-, 3-, and 5-minute time points after treadmill testing in 2,193 males being evaluated for chest pain at the Palo Alto and Long Beach VA Hospitals. Left ventricular ejection fraction (LVEF) was calculated using biplane ventriculography and patients were considered to have LVSD if they had an LVEF <50%. Angiographic and clinical data was available for all patients. Of the 2,193 patients, 314 patients had LVSD and 109 had a history of HF. Both HF patients and patients with LVSD with a normal HRR at 2 minutes had improved survival compared with patients that had an abnormal HRR at 2 minutes when adjusted for age and beta-blocker use (HF adjusted odds ratio 0.25, 95% CI 0.10-0.66, P < .006; LVSD alone adjusted odds ratio 0.25, 95% CI 0.13-0.47, P < .0001). Stepwise proportional hazard regression analysis revealed that only 2-minute HRR, age, LVEF, and chronic obstructive pulmonary disorder were significant predictors of mortality in patients with LVSD and only HRR at 2 minutes and LV hypertrophy were significant predictors of mortality in patients with HF.HRR is a significant predictor of mortality in patients with HF and patients with LVSD and may be useful in better determining prognosis.

Abstract

Many electrocardiographic (ECG) criteria for left ventricular hypertrophy (LVH) exist, but few studies have compared their relative prognostic value for predicting cardiovascular (CV) mortality.We analyzed the first ECG on 46950 consecutive veterans. We targeted male outpatients with a body mass index > 20 to avoid confounding by complicating catabolic illnesses and further excluded those with conduction abnormalities. Using Cox regression models adjusted for age, heart rate, and body mass index, we compared the hazard ratios (HRs) for CV mortality obtained from seventeen commonly used ECG criteria for LVH.During a mean follow-up of 7 +/- 4 years, in a total population of 19434 patients (mean age 54 +/- 14 years), 1254 (6%) patients died of CV causes. The adjusted HR for CV mortality ranged from 1.4 (95% CI 1.2-1.6) to 3.7 (95% CI 2.7-5.0) among the various criteria. Left ventricular hypertrophy defined by composite criteria was generally associated with higher adjusted HRs compared with voltage-only criteria. Among patients with ECG-LVH, the presence of a left ventricular strain pattern or increased negative P-terminal force were most predictive of CV mortality (HR 3.9 and 3.5, 95% CI 3.3-4.6 and 2.8-4.2).Compared with voltage-only criteria for detecting LVH, composite ECG criteria are more strongly predictive of CV mortality. By applying these ECG criteria into routine clinical practice, individuals with LVH who are at higher risk for CV mortality can be identified and appropriately treated.

Abstract

ST depression and T-wave amplitude abnormalities are known to be independent predictors of cardiovascular (CV) death, but a direct comparison between them has not been described.Analyses were performed on the first electrocardiogram (ECG) digitally recorded on 46,950 consecutive patients at the Palo Alto Veterans Affairs Medical Center since 1987. Females and patients with electrocardiograms exhibiting bundle branch block, left ventricular hypertrophy, electronic pacing, diagnostic Q waves, or Wolff-Parkinson-White syndrome were excluded, leaving 31,074 male patients for analysis (mean age 55 +/- 14). There were 1878 (6.0%) cardiovascular deaths (mean follow-up of 6 +/- 4 years). Electrocardiograms were classified using Minnesota code according to the degree of ST depression and T-wave abnormality, and the nine possible combinations of ST segment and T-wave abnormalities were recoded for analysis.The combination of major abnormalities in ST segments and T-waves carried the greatest hazard [3.2 (CI 2.7-3.8)]. Minor ST depression combined with more severe T-wave abnormalities carried a hazard of 3.1 (CI 2.5-3.7), whereas minor T-wave abnormalities combined with more severe ST depression carried a hazard of only 1.9 (CI 1.6-2.3).While both ST segment depression and abnormal T-wave amplitude are clinically important, T-wave abnormalities appear to be greater predictors of cardiovascular mortality.

Abstract

A number of electrocardiogram (ECG) classification systems have been developed to estimate cardiac injury, infarct size, and left ventricular function. Although many studies have documented an association between clinical, imaging, and autopsy data, few have evaluated their prognostic value.ECGs from 46,933 patients were analyzed using computerized measurements and algorithms. The Simplified Selvester Score, the Cardiac Infarction Injury Score (CIIS), and a Q-wave score were calculated. Other ECG characteristics such as left ventricular hypertrophy and bundle-branch blocks were also evaluated. The main outcome was cardiovascular (CV) mortality. During a mean follow-up of 6 years, the CIIS outperformed all other ECG classifications in determining prognosis. Going from lowest to highest tertile of CIIS, each step had a hazard ratio of 1.39 (CI 1.32-1.45) or a 39% increase in risk per tertile. Using clinically based thresholds, the annual mortality for high-risk CIIS was 4.5% (CI 4.0-4.6) versus 0.3% (CI 0.0-1.3) for those in the low-risk group.A low-risk damage score was associated with a <1% annual CV mortality and a high-risk damage score with annual CV mortality of >4%. A damage score should be calculated as part of all computerized ECG interpretations.

Abstract

Computerized electrocardiograms recorded on 46,950 male veterans were analyzed to demonstrate the prognostic value of T-wave amplitude in a general medical population. There were 3,926 cardiovascular deaths over 6 years. Multivariate survival analysis allowed the development of a T-wave amplitude graphic that provides clinicians with a simple method of estimating the relative risk for cardiovascular mortality from T-wave amplitude in limb lead I.

Abstract

The purpose of this study was to validate the prognostic value of computer-derived measurements of the spatial alignment of ventricular depolarization and repolarization from the standard 12-lead ECG in a general medical population.Analyses were performed on the first ECG digitally recorded from 46,573 consecutive patients since 1987. QRS and T vector were synthesized by deriving XYZ leads from the 12 leads using the inverse Dower weighting matrix. Subset analyses were considered in patients with and those without standard ECG diagnoses (i.e., atrial fibrillation, Q waves, left ventricular hypertrophy, prolonged QRS duration). The main outcome measure was cardiovascular mortality.During a mean follow-up of 6 years, 4,127 cardiovascular deaths occurred. After adjusting for age, heart rate, and gender in a Cox regression analysis, spatial QRS-T angle was the most significant predictor of cardiovascular mortality, outperforming all other ECG measurements and diagnostic statements. In the subset with ECGs free of any standard diagnoses, annual cardiovascular mortality was 0.8% for normal (0-50 degrees ), 2.3% for borderline (50-100 degrees ), and 5.1% for abnormal (100-180 degrees ) QRS-T angle groups. The borderline and abnormal angle groups had 1.5- and 1.9-fold higher risk, respectively, relative to the normal QRS-T angle group after adjustment for age, gender, and heart rate. Similar results were found when patients with standard ECG diagnosis were included or compared.Spatial QRS-T angle is a significant and independent predictor of cardiovascular mortality that provides greater prognostic discrimination than any of the commonly utilized ECG diagnostic classifications.

Abstract

Exercise testing commonly used by clinicians to characterize cardiovascular risk by detecting myocardial ischemia and assessing response to exercise. However, a consensus has not previously existed regarding the significance of exercise test-induced arrhythmias due to conflicting results from the available studies. Recent studies with longer follow-up and improved technology have therefore stimulated this current review of the topic. Despite the continued debate in the literature regarding the prognosis of ETIA in a general population, there is sufficient evidence to suggest that clinicians should closely evaluate and follow those patients with arrhythmias during exercise testing and aggressively modify risk factors for coronary artery disease.

Abstract

High-sensitivity C-reactive protein (hsCRP) has been shown to be indicative of elevated risk of cardiovascular disease (CVD). We examined this blood marker in persons with spinal cord injury (SCI) in order to determine its potential for predicting elevated cardiac risk.In a cross-sectional analysis, we examined the relationship between hsCRP and insulin resistance and metabolic syndrome among 93 individuals with SCI (50.2 +/- 13 years). Fasting lipids, insulin, glucose, plasma hsCRP, and anthropometric data were gathered from each subject. Comparisons were made with population reference values.Metabolic syndrome and insulin resistance were present in nearly one quarter of the SCI population (22.6%). Subjects with fasting insulin resistance had significantly higher mean hsCRP (4.29 +/- 3.25 mg/L) than those who were not insulin resistant (2.24 +/- 2.02) (P < 0.05). Moreover, hsCRP was significantly elevated in individuals who presented with high cardiovascular risk including severe dyslipidemia (> or = 4 abnormal lipid values) and Framingham Risk scores < or = 6 (P < 0.05 for both values). In addition, the homeostasis model assessment of insulin resistance was mildly correlated with hsCRP (r = 0.33).In individuals with SCI who are insulin resistant and/or display components of the metabolic syndrome, hsCRP is elevated suggesting a clinically important association with cardiovascular risk in this population.

Abstract

Exercise-induced ventricular arrhythmias (EIVA) are frequently observed during exercise testing. However, the clinical guidelines do not specify their significance and so we examined this issue in our population.A retrospective analysis of prospectively collected data was performed on 5754 consecutive male veterans referred for exercise testing at two university-affiliated Veterans Affairs Medical Centers. Exercise test responses were recorded and cardiovascular mortality was assessed after a mean follow-up of 6 +/- 4 years. EIVA were defined as frequent premature ventricular complexes (PVCs) constituting more than 10% of all ventricular depolarizations during any 30-second ECG recording, or a run of three or more consecutive PVCs during the exercise test or recovery.EIVA occurred in 426 patients (7.4%). There were 550 (10.6%) cardiovascular deaths during follow-up. Seventy two (17%) patients with EIVA died of cardiovascular causes, whereas 478 (9.0%) of patients without EIVA died of cardiovascular causes (P < 0.001). Patients with EIVA had a higher prevalence of cardiovascular disease, resting PVCs, resting ST depression, and ischemia during exercise than patients without EIVA. In a Cox hazards model adjusted for age, cardiovascular disease, exercise-induced ischemia, ECG abnormalities, exercise capacity and risk factors, EIVA was significantly associated with time to cardiovascular death. The combination of both resting PVCs and EIVA was associated with the highest hazard ratio.EIVA are independent predictors of cardiovascular mortality after adjusting for other clinical and exercise test variables; combination with resting PVCs carries the highest risk.

Abstract

With increasing research on vulnerable plaques and uncertainty regarding which lesions require revascularization, the goal of this review is to clarify the indications for percutaneous coronary intervention and discuss which lesions do not warrant treatment by intervention. This paper also briefly reviews the potential advantages and limitations of technology that may enable detection of atherosclerotic plaques that are prone to rupture and discusses the future utility of these technologies in prevention of acute coronary syndromes. Providing an evidence-based understanding of lesion morphology and clinical variables that influence outcome enables the interventional cardiologist to determine which atherosclerotic plaques require PCI.

Abstract

While the beneficial effect of exercise capacity on mortality is well-accepted, its effect on health-care costs remains uncertain. This study investigates the relationship between exercise capacity and health-care costs.The Veterans Affairs Health Care System recently implemented a Decision Support System that provides data on patterns of care, patient outcomes, workload, and costs. Total inpatient and outpatient costs were derived from existing administrative and clinical data systems, were adjusted for relative value units, and were expressed in relative cost units. We used univariable and multivariable analyses to evaluate the 1-year total costs in the year following a standard exercise test. Costs were compared with exercise capacity estimated in metabolic equivalents (METs), other test results, and clinical variables for 881 consecutive patients who were referred for clinical reasons for treadmill testing at the Palo Alto Veterans Affairs Health Care System facility between October 1, 1998, and September 30, 2000.The patients had a mean age of 59 years, 95% were men, and 74% were white. Eight patients (< 1%) died during the year of follow-up. Exercise testing showed an average maximum heart rate of 138 beats/min, 8.2 METs, and a peak Borg scale of 17. In unadjusted analysis, costs were incrementally lower by an average of 5.4% per MET increase (p < 0.001). In a multivariable analysis adjusting for demographic variables, treadmill test performance and results, and clinical history, METs were found to be the most significant predictor of cost (F-statistic, 21.8; p < 0.001).These findings are consistent with the hypothesis that exercise capacity is inversely associated with health-care costs.

Abstract

Among the most compelling challenges facing cardiologists today is identification of which patients are at highest risk for sudden death. Automatic implantable cardioverter-defibrillators are now indicated in many of these patients, yet the role of noninvasive risk stratification in classifying patients at high risk is not well defined. The purpose of this review is to evaluate the various electrocardiographic (ECG) techniques that appear to have potential in assessment of risk for arrhythmia. The resting ECG (premature ventricular contractions, QRS duration, damage scores, QT dispersion, and ST segment and T wave abnormalities), T wave alternans, late potentials identified on signal-averaged ECGs, and heart rate variability are explored. Unequivocal evidence to support the widespread use of any single noninvasive technique is lacking; further research in this area is needed. It is likely that a combination of risk evaluation techniques will have the greatest predictive power in enabling identification of patients most likely to benefit from device therapy.

Effect of age and end point on the prognostic value of the exercise testCHESTYamazaki, T., Myers, J., Froelicher, V. F.2004; 125 (5): 1920-1928

Abstract

The clinical and exercise test variables chosen for predicting prognosis vary in the available studies. This could be due to the effect of age of the patients tested and the choice of outcomes used as end points in these follow-up studies.To evaluate the effect of age and end points on exercise test variables chosen as significantly and independently associated with time to death.Analyses were performed on the first treadmill test performed on consecutive male veterans at the Palo Alto and Long Beach Veterans Affairs Medical Centers since 1987. After removal of patients with congestive heart failure, coronary interventions, left bundle-branch block, atrial fibrillation, myocardial infarction and/or Q wave, and digoxin use, 3,745 male subjects remained. The outcomes were cardiovascular and all-cause mortality. The study population was divided into subsets according to age; exercise test and clinical variables were analyzed within the age subsets using the Cox hazard model.The mean age at the time of testing was 57 +/- 12 years (+/- SD) and they were followed up for a mean of 6.6 years. There were 544 all-cause deaths, with 206 of the deaths being due to cardiovascular causes (38%). When the study group was classified into subsets based on age, exercise capacity (in metabolic equivalents [METs]) was chosen by the Cox hazard model most consistently in the age groups using either end point. Even when age was added to the Duke treadmill score, prediction of death did not improve in those > 70 years of age because of the nonlinear relationship between age, the exercise test variables, and time to death. The most important age cut points for clinically important differences in exercise test predictors appeared to be 70 years and 75 years of age. In the patients 70 to 75 years of age, peak METs was the only variable predictive of all-cause mortality, and exercise-induced ST-segment depression was the only predictor of cardiovascular death; in the patients > 75 years of age, none of the exercise test responses were predictive of either death outcome.Both age and the outcome selected as an end point affect the exercise test responses chosen for scores to predict prognosis. Differences in age of the subjects tested and/or the outcome selected as the end point can explain the differences in the studies using exercise testing to predict prognosis.

Abstract

This study seeks to further characterize the role of exercise testing in the elderly for prognosis and diagnosis of coronary artery disease.Recent exercise testing guidelines have recognized that statements regarding the elderly do not have an adequate evidence-based quality because the studies they are based on have limitations in sample size and design. The Duke Treadmill Score has been recommended for risk stratification, but recent evidence has suggested that it does not function in the elderly.The study population consisted of male veterans (1872 patients >or=65 years; 3798 patients <65 years) who underwent routine clinical exercise testing with a mean follow-up of six years. A subset who underwent coronary angiography as clinically indicated (elderly, n = 405; younger, n= 809) were included. The primary outcome for all subjects was cardiovascular mortality with coronary angiographic findings as the outcome in those selected for angiography.In survival analysis, exercise-induced ST depression was prognostic in both age groups only when cardiovascular death was considered as the end point. Peak metabolic equivalents were the most significant predictor for both age groups only when all-cause death was considered as the end point. New age-specific prognostic scores were developed and found to be predictive for cardiovascular mortality in the elderly. Moreover, in the angiographic subset of the elderly, a specific diagnostic score provided significantly better discrimination than exercise ST measurements alone. For any new score, there is a need for validation in another elderly population.The mortality end point affected the choice of prognostic variables. This study demonstrates that exercise test scores can be helpful for the diagnosis and prognosis of coronary disease in the elderly.

Abstract

We examined the prognostic value of computerized measurements of QT dispersion in 37,579 male veterans. The results of our study showed that QT dispersion is a poor independent predictor of cardiovascular mortality.

Importance of the first two minutes of heart rate recovery after exercise treadmill testing in predicting mortality and the presence of coronary artery disease in menAMERICAN JOURNAL OF CARDIOLOGYLipinski, M. J., Vetrovec, G. W., Froelicher, V. F.2004; 93 (4): 445-449

Abstract

We retrospectively analyzed exercise treadmill and coronary angiographic data of 2,193 men to compare heart rate (HR) recovery with angiographic and mortality data during a follow-up study of 7 +/- 2.7 years. Only the first 2 minutes of HR recovery predicted mortality (p <0.001), and the HR decrease during the second minute of recovery predicted the presence of coronary artery disease (p <0.05).

Abstract

Ethnic differences in the relationship between access to health care and survival are difficult to define because of many confounding factors, such as socioeconomic status and baseline differences in health. Because the Veterans Affairs health care system offers health care largely without financial considerations, it provides an ideal setting in which to identify and understand ethnic differences in health outcomes. Previous studies in this area have lacked clinical and cardiovascular data with which to adjust for baseline differences in patients' health.Data were collected from consecutive men referred for resting electrocardiography (ECG) (n = 41 087) or exercise testing (n = 6213) during 12 years. We compared ethnic differences in survival between whites, blacks, and Hispanics after considering baseline differences in age and hospitalization status. We also adjusted for electrocardiogram abnormalities and cardiac risk factors, exercise test results, and cardiovascular comorbidities.White patients tended to be older and had more baseline comorbidities and cardiovascular interventions when they presented for testing. White patients had increased mortality rates compared with blacks and Hispanics. In the ECG population, after adjusting for demographics and baseline electrocardiogram abnormalities, Hispanics had improved survival compared with whites and blacks. In the exercise test population, after adjusting for the same factors, as well as adjusting for the presence of cardiovascular comorbidities, cardiac risk factors, and exercise test findings, Hispanics also exhibited improved survival compared with the other 2 ethnicities. There were no differences in mortality rates between whites and blacks.Our findings demonstrate that the health care provided to veterans referred for routine ECG or exercise testing is not associated with poorer survival in ethnic minorities.

Abstract

The purpose of this study was to determine the prevalence and prognostic significance of exercise-induced ventricular arrhythmias (EIVAs) in patients referred for exercise testing, considering the arrhythmic substrate and exercise-induced ischemia.EIVAs are frequently observed during exercise testing, but their prognostic significance is uncertain. The design of this study was a retrospective analysis of prospectively collected data, and it took place in 2 university-affiliated Veterans Affairs Medical Centers. Patients comprised 6213 consecutive males referred for exercise tests. We measured clinical exercise test responses and all-cause mortality after a mean follow-up of 6 +/- 4 years. EIVAs were defined as frequent premature ventricular contractions (PVCs) constituting >10% of all ventricular depolarizations during any 30 second electrocardiogram recording, or a run of > or =3 consecutive PVCs during exercise or recovery.A total of 1256 patients (20%) died during follow-up. EIVAs occurred in 503 patients (8%); the prevalence of EIVAs increased in older patients and in those with cardiopulmonary disease, resting PVCs, and ischemia during exercise. EIVAs were associated with mortality irrespective of the presence of cardiopulmonary disease or exercise-induced ischemia. In those without cardiopulmonary disease, mortality differed more so later in follow up than earlier. In those without resting PVCs, EIVAs were also predictive of mortality, but in those with resting PVCs, poorer prognosis was not worsened by the presence of EIVAs.Exercise induced ischemia does not affect the prognostic value of EIVAs, whereas the arrhythmic substrate does. EIVAs and resting PVCs are both independent predictors of mortality after consideration of other clinical and exercise-test variables. These findings are of limited clinical significance because of the modest change in risk and the lack of any established intervention. However, they explain some of the previous controversy and highlight the need to consider resting PVCs and follow-up duration in assessing the clinical implications of EIVAs.

Abstract

The authors evaluate the prognostic value of treadmill testing in a large consecutive series of patients with chronic coronary artery disease. Exercise testing is widely performed, but analyses of the prognostic value of test results have largely concentrated on patients referred for the diagnosis of coronary artery disease, patients after an acute coronary event or procedure, or patients with congestive heart failure.All patients referred for evaluation at two university-affiliated Veterans Affairs Medical Centers who underwent exercise treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security Death Index after a mean 5.8-year follow-up. Patients without established heart disease and those with congestive heart failure were excluded, leaving the target population of those with a history myocardial infarction or coronary intervention. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. All-cause mortality was used as the endpoint for follow-up. Standard survival analysis was performed including Kaplan Meier curves and the Cox Hazard Model.Of the 1,473 patients with coronary artery disease who had exercise testing, 273 (19%) patients had a revascularization procedure (Revascularization group); 813 (55%) had a history of myocardial infarction, diagnostic Q waves (MI group), or both; and 387 (26%) had a history of myocardial infarction or Q wave and revascularization (Combined group). Mean age of the patients was 61.8 +/- 9 years. A total of 401 deaths occurred during a mean follow-up of 5.8 years with an annual mortality rate of 4.5%. Only two variables, age and maximal exercise capacity, were independently and statistically associated with time to death in all three groups and were the strongest predictors of all cause mortality.A simple score based on METs, age, and history of myocardial infarction or diagnostic Q waves can stratify prognosis in patients with chronic coronary artery disease. The score enabled the identification of a group at low risk (32% of the cohort) with an annual mortality rate of 2%, a group at intermediate risk (42% of the cohort) with an annual mortality rate of about 4%, and a group at high risk (26% of the cohort) with an average annual mortality rate of approximately 7%.

Abstract

Recently revised American College of Cardiology/American Heart Association guidelines for exercise electrocardiography (ExECG) have suggested that ExECG scores be used to assist in management decisions in patients with suspected coronary artery disease (CAD).We used 442 women who underwent both ExECG and coronary angiography (CAD > or =1 lesion with > or =50% stenosis; CAD prevalence was 32%) to derive an ExECG score including clinical and ExECG variables. By use of logistic regression analysis, variables were selected and relative weights were determined. Variable codes multiplied by respective weights were summed to produce a final ExECG score. The score was validated in separate populations concerning angiographic as well as prognostic end points.Clinical variables selected and their weights included age (5), symptoms (2), diabetes (2), smoking (2), and estrogen status (1). ExECG variables selected and their weights included ST depression (2), exercise heart rate (4), and Duke Angina Index (3). For the validation group, score ranges are shown with the prevalence of CAD: <20 = 0/5 or 0%, 20-29 = 3/26 or 11%, 30-39 = 20/56 or 36%, 40-49 = 33/81 or 41%, 50-59 = 24/49 or 49%, 60-69 = 22/32 or 69%, and >70 = 7/7 or 100%. Frequency of death within 3 predetermined subgroups was as follows: low <40 = 3/1237 (0.2%), intermediate 40-60 = 9/383 (2.3%), high >60 = 4/54(7%); P

Abstract

To evaluate the prognostic characteristics of body mass index (BMI) and standard exercise test variables in a consecutive series of patients with mild to moderate congestive heart failure (CHF) referred for standard exercise tests.Controversy exists regarding the prognostic importance of BMI, etiology, and exercise test variables in patients with CHF.All patients referred for evaluation at two university-affiliated Veterans Affairs Medical Centers who underwent treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security Death Index after a mean 6 years follow-up. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. Survival analysis was performed using all-cause mortality as the endpoint for follow-up.A total of 522 patients with a history and clinical findings of CHF underwent exercise testing. Forty-two percent died during the follow-up period, for an average annual mortality of 6.7%. Cox proportional hazards model chose peak metabolic equivalents (METs), BMI, age, and ischemic etiology in rank order as independently and significantly associated with time to death. A score based on these variables classified patients into low (2% annual mortality), medium (5.2%), and high-risk groups (7% annual mortality).Standard exercise testing and BMI can be used to estimate prognosis in outpatients with heart failure. A score incorporating METs, BMI, age, and etiology efficiently stratified these patients. BMI was chosen by the survival analysis, confirming its surprising inverse relationship to prognosis in CHF patients (i.e., heavier patients do better).

Abstract

To demonstrate the prevalence and prognostic value of electrocardiographic abnormalities in patients with chronic spinal cord injury.All electrocardiographs obtained in the Palo Alto Veterans Affairs Medical Center since 1987 have been digitally recorded and stored in a computerized database. For this study, only the first electrocardiograph was considered for analysis. The subjects were divided according to age and level of spinal cord injury. The Social Security Death Index was used to ascertain vital status as of December 1999.Annual mortality was similar in those with chronic spinal cord injury and the able-bodied. However, individuals with a higher level of injury had a significantly higher death rate than those with a lower level of injury. The prognostic characteristics of electrocardiographic abnormalities were similar in both the able-bodied and those with spinal cord injury.In general, electrocardiographic abnormalities had the same prevalence in the spinal cord injury subjects as in the able-bodied ones. The prognostic value of electrocardiographic abnormalities in subjects with spinal cord injury is similar to that observed in able-bodied subjects.

Abstract

The application of common statistical techniques to clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners function as gatekeepers and decide which patients must be referred to the cardiologist, they need to optimally use the basic tools they have available (i.e., history, physical exam, and the exercise test).Review of the literature with a focus on the scientific techniques for aiding the decision-making process.Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power when compared using receiver-operating-characteristic curves with the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers as part of information management systems can calculate complicated equations to provide scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Scores have also been compared with physician judgment and been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists, and often better than nonspecialists.Multivariate scores can empower the clinician to assure the cardiac patient with access to appropriate and cost-effective cardiological care.

Abstract

Although several diagnostic modalities are available to the clinician interested in diagnosing coronary artery disease, very few have been validated in diabetic populations. This review discusses the non-invasive diagnosis of coronary disease in diabetic patients. Evidence regarding the prevalence and prognostic significance of silent ischemia is reviewed and the potential impact of silent ischemia on the diagnostic characteristics of the exercise treadmill test discussed. Other diagnostic tools are considered, and recommendations are made with respect to screening asymptomatic diabetic patients for coronary artery disease.

Abstract

Our purposes were to compare the responses to exercise testing in elderly (> or =65 years of age) and younger men, and to investigate whether exercise testing has similar prognostic value in the two age groups.We included all elderly (n = 1185) and younger (n = 2789) male veterans without established coronary heart disease who underwent routine clinical exercise testing between 1987 and 2000 at two academically affiliated Veteran's Affairs medical center laboratories. Measurements included a standardized medical history, exercise testing, and all-cause mortality.Compared with younger patients, elderly patients achieved a lower workload (a mean [+/- SD] of 7 +/- 3 vs. 10 +/- 4 metabolic equivalents [METs], P <0.001) and were more likely to have abnormal ST depression (27% [n = 324] vs. 16% [n = 436], P <0.001). During the mean follow-up of 6 years, annual mortality was twice as high among elderly patients as among younger patients (4% vs. 2%, P <0.001). The only exercise test variable that was associated significantly with time to death in both age groups was maximal METs achieved: each 1 MET increase in exercise capacity was associated with an 11% reduction in annual mortality. Exercise-induced ST depression was more common in those who subsequently died, but was not an independent predictor of mortality.In elderly men, exercise testing provided prognostic information incremental to clinical data. Achieved workload (in METs) was the major exercise testing variable associated with all-cause mortality. Its prognostic importance was the same in elderly as in younger men.

Abstract

Our purpose was to compare exercise test scores and ST measurements with a physician's estimation of the probability of the presence and severity of angiographic disease and the risk of death. The American College of Cardiology/American Heart Association exercise testing guidelines provide equations to calculate treadmill scores and recommend their use to improve the predictive accuracy of the standard exercise test. However, if physicians can estimate the probability of coronary artery disease and prognosis as well as the scores, there is no reason to add this complexity to test interpretation.A clinical exercise test was performed and an angiographic database was used to print patient summaries and treadmill reports. The clinical/treadmill test reports were sent to expert cardiologists and to 2 other groups, including randomly selected cardiologists and internists. They classified the patients summarized in the reports as having a high, low, or intermediate probability for the presence of any severe angiographic disease and estimated a numerical probability from 0% to 100%. The Social Security Death Index was used to determine survival status of the patients.Twenty-six percent of the patients had severe angiographic disease, and the annual mortality rate for the population was 2%. Forty-five expert cardiologists returned estimates on 473 patients, 37 randomly chosen practicing cardiologists returned estimates on 202 patients, 29 randomly chosen practicing internists returned estimates on 162 patients, 13 academic cardiologists returned estimates on 145 patients, and 27 academic internists returned estimates on 272 patients. When probability estimates for presence and severity of angiographic disease were compared, in general, the treadmill scores were superior to physicians' and ST analysis at predicting severe angiographic disease. When prognosis was estimated, treadmill prognostic scores did as well as expert cardiologists and better than most other physician groups.Estimates of the presence of clinically significant and severe angiographic coronary artery disease provided by scores were superior to physician estimates and ST analysis alone. Estimates of prognosis provided by scores were similar to the estimates made by expert cardiologists and more accurate than the estimates made by most other physician groups.

Abstract

There has been controversy over what is the best angiographic luminal dimension criterion associated with ischemia for evaluating diagnostic tests. If one assumes that ST-segment depression or scores are indicators of ischemia, then whatever angiographic criteria best discriminates those with ischemic and nonischemic responses would be the best angiographic marker for ischemia. To study this, we calculated the area under the ROC curves for ST depression and scores at different angiographic cut-points in order to determine the best angiographic cut-point for defining ischemia-producing coronary disease.Twelve hundred and seventy-six consecutive males without prior MI with a mean age of 59 +/- 11 years who had undergone exercise testing and coronary angiography were analyzed in this study. We calculated the number of patients of this population that would be considered to have coronary artery disease at different cut-points for angiographic luminal stenosis. For example, 59% of the patients had significant CAD when disease was defined as 50% or greater coronary lumen stenosis of any coronary vessel while 49% of the patients had significant CAD when disease was defined as 70% or greater coronary lumen stenosis. Cut-points were considered between 40 to 100% coronary lumen stenosis. ROC analysis was then performed comparing ST depression and treadmill scores at each of these cut-points.The cut-point for coronary lumen stenosis that returned the highest AUC for ST depression and scores was between 70 and 80% coronary luminal stenosis. However, the difference between the 50% and 75% luminal stenosis criteria was minimal.It appears that the best cut-point for defining significant angiographic disease when evaluating diagnostic tests of ischemia is 75% or greater coronary luminal stenosis.

Abstract

Recent data suggest that beta-blockers can be beneficial in subgroups of patients with chronic heart failure (CHF). For metoprolol and carvedilol, an increase in ejection fraction has been shown and favorable effects on the myocardial remodeling process have been reported in some studies. We examined the effects of bisoprolol fumarate on exercise capacity and left ventricular volume with magnetic resonance imaging (MRI) and applied a novel high-resolution MRI tagging technique to determine myocardial rotation and relaxation velocity.Twenty-eight patients (mean age, 57 +/- 11 years; mean ejection fraction, 26 +/- 6%) were randomized to bisoprolol fumarate (n = 13) or to placebo therapy (n = 15). The dosage of the drugs was titrated to match that of the the Cardiac Insufficiency Bisoprolol Study protocol. Hemodynamic and gas exchange responses to exercise, MRI measurements of left ventricular end-systolic and end-diastolic volumes and ejection fraction, and left ventricular rotation and relaxation velocities were measured before the administration of the drug and 6 and 12 months later.After 1 year, heart rate was reduced in the bisoprolol fumarate group both at rest (81 +/- 12 before therapy versus 61 +/- 11 after therapy; P

Abstract

The objective was to examine the prevalence of early repolarization in a spinal cord injury (SCI) clinic and the relationship of level of injury to this electrocardiogram (ECG) finding.ST elevation on the resting ECG can be either a normal variant or a sign of acute ischemia, evolving myocardial infarction, or pericarditis. It is frequently seen as a normal variant (early repolarization) in healthy individuals, but has also been reported in individuals with SCI. While the etiology of benign ST elevation (early repolarization) has not been clearly defined, current opinion is that this finding is seen in individuals with high vagal tone.Retrospective analysis was made of 31 5 individuals with SCI at T5 or above (140 with complete injuries), and 1 98 with SCI at T6 or below, and who had ECGs in the computerized database at the Palo Alto VA Medical Center. A comparison cohort of 32,841 able-bodied male controls also was identified in the same ECG database. Patient demographics and computerized ST measurements were analyzed.The prevalence of ST elevation was significantly higher in both the total high-level injury group (19%) and the complete high-injury group (24.5%) than in either the low-injury (6.5%) or control groups (13%), with P < 0.001 for comparisons between both high- and low-injury groups and high injury vs control. The magnitude of ST elevation was also higher in the high-injury groups vs the low-injury and control groups.There is a higher prevalence of early repolarization in individuals with SCI at levels of injury that can disrupt central sympathetic command of the heart. It appears that either enhanced vagal tone or loss of sympathetic tone is responsible for ST elevation.

Abstract

Exercise capacity is known to be an important prognostic factor in patients with cardiovascular disease, but it is uncertain whether it predicts mortality equally well among healthy persons. There is also uncertainty regarding the predictive power of exercise capacity relative to other clinical and exercise-test variables.We studied a total of 6213 consecutive men referred for treadmill exercise testing for clinical reasons during a mean (+/-SD) of 6.2+/-3.7 years of follow-up. Subjects were classified into two groups: 3679 had an abnormal exercise-test result or a history of cardiovascular disease, or both, and 2534 had a normal exercise-test result and no history of cardiovascular disease. Overall mortality was the end point.There were a total of 1256 deaths during the follow-up period, resulting in an average annual mortality of 2.6 percent. Men who died were older than those who survived and had a lower maximal heart rate, lower maximal systolic and diastolic blood pressure, and lower exercise capacity. After adjustment for age, the peak exercise capacity measured in metabolic equivalents (MET) was the strongest predictor of the risk of death among both normal subjects and those with cardiovascular disease. Absolute peak exercise capacity was a stronger predictor of the risk of death than the percentage of the age-predicted value achieved, and there was no interaction between the use or nonuse of beta-blockade and the predictive power of exercise capacity. Each 1-MET increase in exercise capacity conferred a 12 percent improvement in survival.Exercise capacity is a more powerful predictor of mortality among men than other established risk factors for cardiovascular disease.

Abstract

Recently, several treadmill scores have been proposed as means for improving the diagnostic accuracy of the exercise treadmill test (ETT). Questions remain regarding the diagnostic accuracy of treadmill scores when applied to a different patient population than that from which they were derived; furthermore, many treadmill scores have not been compared with one another in the same population.The diagnostic accuracy of treadmill scores may not be the same.A retrospective analysis of data collected prospectively was performed on consecutive patients referred for evaluation of chest pain. All patients underwent a standard ETT followed by coronary angiography. Using angiographic evidence of coronary artery disease (CAD) as a reference, the area under the curve (AUC) of receiver operator characteristic (ROC) plots of the ST response alone, the Duke Treadmill Score (DTS), the Morise score, the Detrano score, the VA score, and a Consensus score consisting of the Morise, Detrano, and VA scores together were calculated and compared. The predictive accuracies of the DTS and the Consensus score to stratify patients for the likelihood of CAD were calculated and compared.In all, 1,282 patients without a prior myocardial infarction had an ETT and coronary angiography. The AUC (+/- standard error) was 0.67+/-0.01 for the ST response, 0.73+/-0.01 for DTS, 0.76+/-0.01 for Detrano score, 0.77+/-0.01 for Morise score, 0.78+/-0.01 for VA score, and 0.78+/-0.01 for Consensus score. The AUC for each treadmill score was significantly higher (z-score > 1.96) than for the ST response alone. The AUC of DTS was significantly lower than all other treadmill scores (z-score > 1.96). The predictive accuracy (+/-95% confidence interval) of the DTS to risk stratify patients into high and low likelihood for CAD was 71 (65-77)%, versus 80 (74-86)% for the Consensus score (p < 0.0001).In this population, the DTS remains useful for diagnosing CAD and stratifying for the likelihood of CAD, although it is less accurate than other treadmill scores.

Abstract

Statistical tools can be used to create scores for assisting in the diagnosis of coronary artery disease and assessing prognosis. General practitioners and internists frequently function as gatekeepers, deciding which patients must be referred to the cardiologist. Therefore, they need to use the basic tools they have available (ie, history, physical examination and the exercise test) in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with diagnosis only using the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a more practical management strategy than a response of normal or abnormal. Although computers, as part of information management systems, can calculate complicated equations and derive these scores, physicians are reluctant to trust them. However, when represented as nomograms or simple additive discrete pieces of information, scores are more readily accepted. The scores have been compared with physician judgment and have been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated METs? Should ST/heart rate index be used instead of putting ST depression and heart rate separately into the models? Should right-sided chest leads and heart rate in recovery be considered? There is a need for further evaluation of these easily obtained variables to improve the accuracy of prediction algorithms, especially in women. The portability and reliability of scores must be ensured because access to specialized care must be safeguarded. Assessment of the clinical and exercise test data and application of the newer scores can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiologic care.

Abstract

Physical activity and symptom questionnaires have been used as surrogates for exercise testing to estimate a patient's functional capacity and to individualize an exercise testing protocol in accordance with exercise testing guidelines. To validate these approaches, they must be compared with measured oxygen uptake (peak VO (2)).Before exercise testing was performed, a brief, self-administered questionnaire (Veterans Specific Activity Questionnaire [VSAQ]) was given to 337 patients referred for exercise testing for clinical reasons. The VSAQ was used to estimate exercise tolerance on the basis of symptoms during daily activities to individualize ramp rates on the treadmill so that the test duration would be approximately 10 minutes. Clinical and demographic variables were added to the VSAQ responses in a stepwise regression model to determine their ability to predict both directly measured peak VO (2) and peak metabolic equivalents (METs) predicted from the treadmill workload.The mean exercise time was 9.6 +/- 3 minutes. Responses to the VSAQ and age were the strongest predictors of both measured and predicted exercise capacity. Small but significant contributions to the explanation of variance in both measured and estimated METs were made by resting heart rate, forced expiratory volume in 1 second expressed as a percentage of normal, exercise capacity predicted for age, and body mass index. The multiple R values from the regression equations for measured and estimated METs were 0.58 and 0.72, respectively.Estimating a patient's symptoms associated with daily activities along with age are the strongest predictors of a patient's exercise tolerance. The VSAQ, combined with pretest clinical data, predicts the estimated MET value from treadmill speed and grade better than directly measured METs do. When used for estimating a patient's symptom limits to individualize ramp rates on a treadmill, this approach yields an appropriate test duration in accordance with recent exercise testing guidelines.

Abstract

The goal of this study was to validate the prognostic value of the drop in heart rate (HR) after exercise, compare it to other test responses, evaluate its diagnostic value and clarify some of the methodologic issues surrounding its use.Studies have highlighted the value of a new prognostic feature of the treadmill test-rate of recovery of HR after exercise. These studies have had differing as well as controversial results and did not consider diagnostic test characteristics.All patients were referred for evaluation of chest pain at two university-affiliated Veterans Affairs Medical Centers who underwent treadmill tests and coronary angiography between 1987 and 1999 as predicted after a mean seven years of follow-up. All-cause mortality was the end point for follow-up, and coronary angiography was the diagnostic gold standard.There were 2,193 male patients who had treadmill tests and coronary angiography. Heart rate recovery at 2 min after exercise outperformed other time points in prediction of death; a decrease of <22 beats/min had a hazard ratio of 2.6 (2.4 to 2.8 95% confidence interval). This new measurement was ranked similarly to traditional variables including age and metabolic equivalents but failed to have diagnostic power for discriminating those who had angiographic disease.Heart rate at 1 or 2 min of recovery has been validated as a prognostic measurement and should be recorded as part of all treadmill tests. This new measurement does not replace, but is supplemental to, established scores.

Abstract

The recent American College of Cardiology/American Heart Association exercise testing guidelines provided equations to calculate treadmill scores and recommended their use to improve the predictive accuracy of the standard exercise test. However, if physicians can estimate the probability of coronary artery disease as well as the scores can, there would be no reason to add this complexity to test interpretation. To compare the exercise test scores with physician's estimation of disease probability, we used clinical, exercise test, and coronary angiographic data to compute the recommended scores and print patient summaries and treadmill reports.To determine whether exercise test scores can be as effective as expert cardiologists in diagnosing coronary disease.Five hundred ninety-nine consecutive male patients without previous myocardial infarction with a mean +/- SD age of 59 +/- 11 years were considered for this analysis. With angiographic disease defined as any coronary lumen occlusion of 50% or more, 58% had disease. The clinical/treadmill test reports were sent to expert cardiologists and to 2 other groups, including randomly selected cardiologists and internists, who classified the patients as having high, low, or intermediate probability of disease and estimated a numerical probability from 0% to 100%.Forty-five expert cardiologists returned estimates on 336 patients, 37 randomly chosen practicing cardiologists returned estimates on 129 patients, 29 randomly chosen practicing internists returned estimates on 106 patients, 13 academic cardiologists returned estimates on 102 patients, and 27 academic internists returned estimates on 174 patients. When probability estimates were compared, the scores were superior to all physician groups (0.76 area under the receiver operating characteristic curve to 0.70 for experts [P=.046], 0.73 to 0.58 for cardiologists [P=.003], and 0.76 to 0.61 for internists [P=.006]). Using a probability cut point of greater than 70% for abnormal, predictive accuracy was 69% for scores compared with 64% for experts, 63% to 62% for cardiologists, and 70% to 57% for internists.Although most similar to the disease estimates of the presence of clinically significant angiographic coronary artery disease provided by the expert cardiologists, the scores outperformed the nonexpert physicians.

Abstract

To report the prevalence of abnormal treadmill test responses and their association with mortality in a large consecutive series of patients referred for standard exercise tests, with testing performed and reported in a standardized fashion.Exercise testing is widely performed, but few databases exist of large numbers of consecutive tests performed on patients referred for routine clinical purposes using standardized methods. Even fewer of the available databases have information regarding all-cause mortality as an outcome.All patients referred for evaluation at two university-affiliated Veterans Affairs medical centers who underwent exercise treadmill testing for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security death index after a mean 6.2 years (median, 7 years) of follow-up. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. All-cause mortality was utilized as the end point for follow-up. Standard survival analysis was performed, including Kaplan-Meier curves and a Cox hazard model.There were 6,213 male patients (mean +/- SD age, 59 +/- 11 years) who underwent standard exercise ECG treadmill testing over the study period with a mean follow-up duration of 6.2 +/- 3.7 years. There were no complications of testing in this clinically referred population, 78% of whom were referred for chest pain, or risk factors or signs or symptoms of ischemic heart disease. Overlapping thirds had typical angina or history of myocardial infarction (MI). Five hundred seventy-nine patients had prior coronary artery bypass surgery, and 522 patients had a history of congestive heart failure (CHF). Indications for testing were in accordance with published guidelines. Twenty percent died over the follow-up period, for an average annual mortality rate of 2.6%. Cox hazard function chose the following variables in rank order as independently and significantly associated with time to death: exercise capacity (metabolic equivalents < 5, age > 65 years, history of CHF, and history of MI. A score based on these variables (summing up the four variables [if yes = 1 point]) classified patients into low-risk, medium-risk, and high-risk groups. The high-risk group (score > or = 3) has a hazard ratio of 5.0 (95% confidence interval, 4.7 to 5.3) and a 5-year mortality rate of 31%.This comprehensive analysis provides rates of various abnormal responses that can be expected in patients referred for exercise testing at a typical medical center. Four simple variables combined as a score powerfully stratified patients according to prognosis.

Abstract

Our purpose was to report the prevalence of abnormal treadmill test responses and their association with mortality in a large consecutive series of patients referred for standard diagnostic exercise tests, with testing performed and reported in a standardized fashion.Exercise testing is widely performed, but an analysis of responses has not been presented for a large number of consecutive tests performed on patients referred for diagnosis of cardiac disease.All patients referred for evaluation at 2 university-affiliated Veterans Affairs Medical Centers who underwent exercise treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive according to the Social Security Death Index after a mean 5.9-year follow-up. Patients with established heart disease (ie, prior coronary bypass surgery, myocardial infarction, or congestive heart failure) were excluded from analyses. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion with a computer-assisted protocol. All-cause mortality was used as the end point for follow-up. Standard survival analysis was performed, including Kaplan-Meier curves and a Cox hazard model.After the exclusions, 3974 men (mean age 57.5 +/- 11 years) had standard diagnostic exercise testing over the study period with a mean of 5.9 (+/-3.7) years of follow-up (64% of all tested). There were no complications of testing in this clinically referred population, 82% of whom were referred for chest pain, risk factors, or signs and symptoms of ischemic heart disease. Five hundred forty-nine (14%) had a history of typical angina. Indications for testing were in accordance with published guidelines. A total of 545 died, yielding an annual mortality rate of 1.8%. The Cox hazard model chose the following variables in rank order as independently associated with time to death: change in rate pressure product, age greater than 65 years, METs less than 5, and electrocardiographic left ventricular hypertrophy. A score based on these variables classified patients into low-, medium-, and high-risk groups. The high-risk group with a score greater than 3 has a hazard ratio of 4 (95% confidence interval 3.82-4.27) and an annual mortality rate of 4%.This comprehensive analysis provides rates of various abnormal responses that can be expected in men referred for diagnostic exercise testing at typical Veterans Administration Medical Centers. Four simple variables combined as a score predict all-cause mortality after clinical decisions for therapy are prescribed.

Abstract

Our purpose was to assess the diagnostic characteristics of the exercise test in patients who fail to reach conventional target heart rates and in patients on beta-blockers.Exercise test results are often considered "inadequate" or "nondiagnostic" in patients taking beta-blockers and in patients who do not achieve 85% of their age-predicted maximal heart rate.The results of exercise tests and coronary angiography performed to evaluate chest pain in 1282 male patients without a prior history of myocardial infarction, coronary revascularization, diagnostic Q wave on the baseline electrocardiogram, or previous cardiac catheterization were analyzed with respect to beta-blocker exposure and failure to reach 85% age-predicted maximal heart rate. Sensitivity, specificity, and predictive accuracy of exercise testing, as well as area under the curve for the receiver operating characteristic plots were calculated for these subgroups with use of coronary angiography as the reference. The angiographic criterion for significant coronary artery disease was 50% narrowing or greater in one or more major coronary arteries.The population was divided into 4 exclusive groups on the basis of whether they reached their target heart rates and whether they were receiving beta-blockers. Sixty to 40 percent of this clinical population failed to reach target heart rate, of which 24% (n = 303) were receiving beta-blockers and 40% (n = 518) were not. The group of patients who reached target heart rate and were not taking beta-blockers was taken as the reference group (n = 409). The group of patients supposedly beta-blocked but who reached the target heart rate (n = 52) had hemodynamic and test characteristics similar to those of the reference group and most likely were not taking their beta-blockers or were not adequately dosed. The prevalence of angiographic coronary disease was significantly higher in the 2 groups failing to reach target heart rate, both in the presence and absence of beta-blockers, compared with the reference group (68% and 64%, respectively, vs 49%, P

Abstract

Given renewed interest in the primary prevention of cardiovascular disease, we comprehensively reviewed the utility of the electrocardiogram (ECG) for screening considering the seminal epidemiologic studies. It appears that conventional risk factors relate to long-term risk, while ECG abnormalities are better predictors of short-term risk. For individual ECG abnormalities as well as for pooled categories of ECG abnormalities, the sensitivity of the ECG for future events was too low for it to be practical as a screening tool. This almost certainly relates to the low prevalence of these abnormalities. However, all ECG abnormalities increase with age and pre-test risk. Also screening with the ECG is of minimal cost and likely to decrease further as stand-alone machines are replaced by integration into personal computers (PC). Another potential impact on performing screening ECGs would be distribution and availability of digitized ECG data via the World Wide Web. For clinical utility of ECG data, comparison with previous ECGs can be critical but is currently limited. PC based ECG systems could very easily replace many of the ECG machines in use that only have paper output. PC-ECG systems would also permit interaction with computerized medical information systems, facilitate emailing and faxing of ECGs as well as storage at a centralized web-server. Web-enabled ECG recorders similar to the new generation of home appliances could follow this quick PC solution. A serious goal for the medical industry should be to end the morass of proprietary ECG digital formats and follow a standardized format. This could lead to a network of web-servers from which every patient's ECGs would be available. Such a situation could have a dramatic effect on the advisability of performing screening ECGs.

Abstract

Our aim was to derive and validate a simplified treadmill score for predicting the probability of angiographically confirmed coronary artery disease (CAD).The American College of Cardiology/American Heart Association guidelines for exercise testing recommend the use of multivariable equations to enhance the diagnostic characteristics of the standard treadmill test. Most of these equations use complicated statistical techniques to provide diagnostic estimates of CAD. Simplified scores derived from such equations that require physicians only to add points have been developed for pretest estimates of disease and for prognosis. However, no simplified score has been developed specifically for the diagnosis of CAD using exercise test results.Consecutive patients referred for evaluation of chest pain who underwent standard treadmill testing followed by coronary angiography were studied. A logistic regression model was used to predict clinically significant (> or = 50% stenosis) CAD and then the variables and coefficients were used to derive a simplified score. The simplified score was calculated as follows: (6 x maximal heart rate code) + (5 x ST-segment depression code) + (4 x age code) + angina pectoris code + hypercholesterolemia code + diabetes code + treadmill angina index code. The simplified score had a range from 6 to 95, with < 40 designated as low probability, between 40 and 60 was intermediate probability, and > 60 was high probability for CAD.A total of 1,282 male patients without a prior myocardial infarction underwent exercise treadmill testing and coronary angiography in the derivation group, and there were 476 male patients in the validation group from another institution. The area under the receiver operating characteristic curve (+/- SE) for the ST-segment response alone was 0.67 as compared to 0.79 +/- 0.01 for the diagnostic score (p > 0.001). The prevalence of significant disease for the men was 27% in the low-probability group, 62% in the intermediate-probability group, and 92% in the high-probability group, which was similar to the prevalence in the validation group, with 22%, 58%, and 92% in low-, intermediate-, and high-probability groups, respectively. The low-probability group had < 4% prevalence of severe disease. In both populations, 7 more patients out of 100 were correctly classified than with the use of ST-segment criteria. When used as a clinical management strategy, the score has a sensitivity of 88% and a specificity of 96%.This simplified exercise score that estimates the probability of CAD can be easily applied without a calculator and is a useful and valid tool that can help physicians manage patients presenting with chest pain.

Abstract

The purpose of this study was to determine the characteristics of exercise treadmill testing in diabetic patients presenting with chest pain.The diagnosis of coronary artery disease (CAD) in diabetic patients is confounded by different manifestations of coronary disease than are seen in the general population. Because of the association of diabetes with accelerated CAD, it is critical to assess the diagnostic utility of the standard exercise test in diabetic patients with chest pain.This study was a retrospective analysis of standard exercise test results in 1,282 male patients without prior myocardial infarction who had undergone coronary angiography and were being evaluated for possible CAD at two Veterans' Administration institutions.In patients with diabetes, 38% had an abnormal exercise test result, and the prevalence of angiographic CAD was 69%; the sensitivity of the exercise test was 47% (95% confidence interval [CI], 41 to 58), and specificity was 81% (95% CI, 68 to 89). In patients without diabetes, 38% had an abnormal exercise test result, and the prevalence of angiographic CAD was 58%; the sensitivity of the exercise test was 52% (95% CI, 48 to 56), and specificity was 80% (95% CI, 76 to 83). The receiver operating characteristic curves were also similar in both diabetic and nondiabetic patients (0.67 and 0.68, respectively).These data demonstrate that the standard exercise test has similar diagnostic characteristics in diabetic as in nondiabetic patients.

Abstract

In the changing economic times, internists and family physicians are becoming the main performers of the standard exercise test. The education of those noncardiologists who wish to perform exercise testing is quite important. In the new millennium, the American College of Cardiology/American Heart Association evidence-based guidelines on exercise testing continue to have a large impact. Used for diagnosis or prognosis, exercise scores such as the Duke exercise score will be applied to each test. Increased computerization and the internet will bring inexpensive web-enabled devices for sophisticated exercise testing into the doctor's office and allow remote over-reading services.

Some common abnormal responses to exercise testing - What to do when you see themPRIMARY CAREEvans, C. H., Froelicher, V. F.2001; 28 (1): 219-?

Abstract

This article reviews the role of exercise testing in the assessment of patients with suspected coronary disease. To accomplish this, four major topics are considered: the general concept of risk stratification; the estimation of outcomes using data from the initial evaluation of the patient; diagnostic assessment with the exercise test; and prognostic assessment with the exercise test. This review focuses on the standard treadmill exercise test.

Abstract

Multivariable analysis of clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners are functioning as gatekeepers and decide which patients must be referred to the cardiologist, they need to use the basic tools they have available (i.e. history, physical examination and the exercise test), in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with simple classification of the ST response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers, as part of information management systems, can run complicated equations and derive these scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Their results have also been compared with physician judgment and found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated metabolic equivalents (METs)? Should ST/heart rate (HR) index be used instead of putting these measurements separately into the models? Should right-sided chest leads and HR in recovery be considered? There is a need for further evaluation of these routinely obtained variables to improve the accuracy of prediction algorithms especially in women. The portability and reliability of these equations must be demonstrated since access to specialised care must be safe-guarded. Hopefully, sequential assessment of the clinical and exercise test data and application of the newer generation of multivariable equations can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiological care.

Abstract

Exercise-induced changes in the electrocardiogram have been used to identify coronary artery disease for almost a century. Over the past decade, however, clinicians have increasingly focused on more expensive diagnostic tools believing them to offer improved diagnostic accuracy. In fact, by incorporating historical data, the simple exercise test can in most cases outperform the newer tests. The use of prediction equations and non-staged exercise protocols can improve the test still further, while advances in the use of the test for prognosis, with the discovery of novel risk factors and the addition of gas analysis, may in the future shift the primary emphasis away from diagnosis. Brief, inexpensive, and done in most cases without the presence of a cardiologist, the exercise test offers the highest value for predictive accuracy of any of the non-invasive tests for coronary artery disease.

Abstract

Congestive heart failure is a chronic, debilitating illness, with increasing prevalence in the elderly. It is one of the most common causes for hospital admission, and associated treatment costs are estimated at $20.2 billion. Despite improved survival with medical therapy, beneficial effects on quality of life have not been consistently reported. In addition, optimum medical therapy, as recommended by evidence-based guidelines, are not always implemented. Counseling and education involving dietary modifications, activity recommendations, medication management, self-monitoring, prognosis, coping skills, social support, caregiver stress, and spiritual needs are critical components in the management of heart failure through initial diagnosis to end of life. Within the last decade, close follow-up for congestive heart failure has been associated with decreased hospitalizations, reduced hospital length of stay, improved functional status, better compliance, lower costs, and improved survival. Research trials have mainly been observational and small, and they have used different interventions. Little has been written regarding outpatient management of the patient with advanced congestive heart failure, and none of the current published guidelines addresses recommendations for the New York Heart Association class IV (other than for transplant candidacy). New models of close follow-up for chronic and advanced congestive heart failure should be investigated. These models could be implemented in urban and rural settings and be supported by private insurance or Medicare.

Abstract

The exercise electrocardiogram remains the noninvasive diagnostic test of first choice in patients with coronary artery disease. While new technology offers novel diagnostic possibilities and the ability to assess patients unsuitable for exercise testing, no other investigation has to this point furnished the quality of functional information and value-for-predictive accuracy of exercise electrocardiography. In this article, we describe how this central position in the work up of the cardiac patient has been secured through the evolution of the microprocessor. Particularly important has been its ability to harness and present large volumes of raw data, to derive and manipulate multivariate equations for diagnostic prediction, and to run 'expert' systems which can pool demographic and exercise test data, calculate risk scores, and prompt the nonexpert with advice on current management. These key features explain the pivotal role of the exercise test in the diagnostic, and increasingly prognostic, armoury of the cardiovascular clinician.

Abstract

Healthcare organizations are being graded in terms of their adherence to practice guidelines. The authors sought information on practice patterns of exercise testing within the Veterans Affairs Health Care System (VAHCS) to determine how well current practice patterns adhere to current guidelines. In addition, we sought to update past surveys to determine methods, indications, utilization of alternative diagnostic modalities, criteria for interpretation, safety, and physician supervision of exercise testing within the VAHCS.Questionnaires were sent to 72 of the largest Veterans Affairs Medical Centers with cardiology divisions. The centers were queried regarding volume and type of exercise testing (standard, nuclear, and echocardiographic), indications, safety, protocols used, and criteria for interpretation.Seventy-one questionnaires were returned, comprising a total of 75,828 exercise tests performed within the last year. Virtually all indications for exercise testing fit the American Heart Association/American College of Cardiology (AHA/ACC) guidelines Class I criteria; 46% of patients were tested for the evaluation of chest pain; 14% were tested to evaluate patients at high risk for coronary artery disease; 10% were preoperative evaluations; and 8% were post-myocardial infarction evaluations. The most commonly used diagnostic test was the standard exercise electrocardiogram; a patient was five times more likely to undergo a standard exercise electrocardiogram or nuclear exercise test than an exercise or pharmacologic echocardiogram. The largest proportion of centers (49%) used 1.0-mm horizontal or downsloping ST depression as a criterion for an abnormal test, although 22% considered 1.5-mm upsloping ST depression to be abnormal, and 25% relied on a treadmill score. Seventy-eight percent of respondents used the treadmill, and of these, 82% used the Bruce or modified Bruce protocol. Four major cardiac events were reported (three myocardial infarctions, one sustained ventricular tachycardia) representing an event rate of 1.2/10,000. A physician was present during 73% of all standard exercise tests; 21% of respondents reported that a physician was required to be present "only for high-risk patients."Indications for exercise testing are in close agreement with the AHA/ACC guidelines; thus, the test continues to have an important role in diagnosis and prognosis among patients with or suspected of having coronary artery disease. The exercise test is an extremely safe procedure, with an event rate similar to other recent surveys. However, a great deal of variation exists in terms of criteria for abnormal results and whether physician presence is required during exercise testing.

The effect of resting ST segment depression on the diagnostic characteristics of the exercise treadmill testJOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGYFearon, W. F., Lee, D. P., Froelicher, V. F.2000; 35 (5): 1206-1211

Abstract

The aim of this study is to demonstrate the effect of resting ST segment depression on the diagnostic characteristics of the exercise treadmill test.Previous studies evaluating the effect of resting ST segment depression on the diagnostic characteristics of exercise treadmill test have been conducted on relatively small patient groups and based only on visual electrocardiogram (ECG) analysis.A retrospective analysis of data collected prospectively was performed on consecutive patients referred for evaluation of chest pain. One thousand two hundred eighty-two patients without a prior myocardial infarction underwent standard exercise treadmill tests followed by coronary angiography, with coronary artery disease defined as a 50% narrowing in at least one major epicardial coronary artery. Sensitivity, specificity, predictive accuracy and area under the curve of the receiver operating characteristic (ROC) plots were calculated for patients with and without resting ST segment depression as determined by visual or computerized analysis of the baseline ECG.Sensitivity of the exercise treadmill test increased in 206 patients with resting ST segment depression determined by visual ECG analysis compared with patients without resting ST segment depression (77 +/- 7% vs. 45 +/- 4%) and specificity decreased (48 +/- 12% vs. 84 +/- 3%). With computerized analysis, sensitivity of the treadmill test increased in 349 patients with resting ST segment depression compared with patients without resting ST segment depression (71 +/- 6% vs. 42 +/- 4%) and specificity decreased (52 +/- 9% vs. 87 +/- 3%) (p < 0.0001 for all comparisons). There was no significant difference in the area under the curve of the ROC plots (0.66-0.69) or the predictive accuracy (62-68%) between the four subgroups.The diagnostic accuracy and high sensitivity of the exercise treadmill test in a large cohort of patients with resting ST segment depression and no prior myocardial infarction support the initial use of the test for diagnosis of coronary artery disease. The classification of resting ST segment depression by method of analysis (visual vs. computerized) did not affect the results.

Abstract

Exercise training is now an accepted therapeutic intervention in patients with reduced ventricular function after a myocardial infarction. However, there are conflicting reports on the effects of training on the remodeling process of the heart, and previous studies have only assessed short-term effects of training.Twenty-five patients with reduced ventricular function after myocardial infarction were randomly assigned to an intensive 2-month exercise training program or to a control group (control group: n = 13, aged 55 +/- 7 years, ejection fraction 33.3% +/- 6%; exercise group: n = 12, aged 56 +/- 5 years, ejection fraction 31.5% +/- 7%) and followed up for 1 year. Measures of left ventricular size, function, and wall thickness in the infarct and noninfarct areas were made by magnetic resonance imaging at baseline, after the 2-month training period, and 1 year later. Maximal oxygen uptake increased in the trained group, from 19.7 +/- 3 mL/kg per minute at baseline to 25.1 +/- 5 and 24.2 +/- 5 mL/kg per minute after 2 months and 1 year, respectively (P

Abstract

To help guide physicians in their evaluation of patients with acute coronary syndromes, we investigated whether elevated cardiac troponin I in patients presenting with unstable angina predicts ischemia on stress testing. Elevated cardiac troponin I in patients who present with chest pain and normal creatine kinase levels is associated with ischemia on stress testing, as well as with future cardiac events.

Abstract

The use of various FES protocols to encourage increases in physical activity and to augment physical fitness and reduce heart disease risk is a relatively new, but growing field of investigation. The evidence so far supports its use in improving potential health benefits for patients with SCI. Such benefits may include more efficient and safer cardiac function; greater stimulus for metabolic, cardiovascular, and pulmonary training adaptations; and greater stimulus for skeletal muscle training adaptations. In addition, the availability of relatively inexpensive commercial FES units to elicit muscular contractions, the ease of use of gel-less, reusable electrodes, and the increasing popularity of home and commercial upper body exercise equipment mean that such benefits are likely to be more accessible to the SCI population through increased convenience and decreased cost. The US Department of Health and Human Services has identified those with SCI as a "special population" whose health problems are accentuated, and so need to be specifically addressed. FES presents "a clear opportunity.... For health promotion and disease prevention efforts to improve the health prospects and functional independence of people with disabilities." As a corollary to this, the Centers for Disease Control and Prevention have recommended the development of techniques to prevent or ameliorate secondary disabilities in persons with a SCI. Patients with SCI have an increased susceptibility to cardiac morbidity and mortality in the acute and early stages of their injury. Most of these patients make an excellent adaptation except when confronted with infection or hypoxia. SCI by itself does not promote atherosclerosis; however, in association with multiple secondary conditions related to SCI, along with advancing age, patients with SCI are predisposed to relatively greater risk of heart disease. The epidemiologic significance of this is reflected in demographic studies that indicate an increasing number of SCI patients becoming aged. Currently 71,000 (40%) of the total 179,000 patients with SCI living in the United States are older than 40 years, and 45,000 have injuries sustained more than 20 years earlier. In addition, new injuries in the older population are increasing (currently 11% of all injuries), and some of these new patients with SCI already have pre-existing cardiac disease. Studies have demonstrated that improved lifestyle, physical activity, lipid management, and dietary restrictions can affect major risk factors for coronary artery disease. Therefore an aggressive cardiac prevention program is appropriate for patients with SCI as part of their rehabilitation. At a given submaximal workload, arm exercise is performed at a greater physiologic cost than is leg exercise. At maximal effort, however, physiologic responses are generally greater in leg exercise than arm exercise. Arm exercise is less efficient and less effective than lower body exercise in developing and maintaining both central and peripheral aspects of cardiovascular fitness. The situation is further compounded in SCI because of poor venous return as a result of lower-limb blood pooling, as a result of lack of sympathetic tone, and a diminished or absent venous "muscle pump" in the legs. This latter mechanism perhaps contributes the greatest diminution in the potential for aerobic performance in the SCI population. Obtaining a cardiopulmonary training effect in individuals with SCI is quite possible. Current studies indicate decreases in submaximal HR, respiratory quotient, minute ventilation, and oxygen uptake, with increases in maximal power output, oxygen uptake, minute ventilation, and lactic acid. Individuals with SCI have been shown to benefit from lower limb functional electrical stimulation (FES)-induced exercise. Studies have consistently reported increases in lower limb strength and cycle endurance performance with these protocols, as well as improvements in metabolic and

Abstract

Currently the standard exercise test is shifting from being a tool for the cardiologist to utilization by the nonspecialist. This change could be facilitated by computerization similar to the interpretation programs available for the resting ECG. Therefore, we sought to determine if computerization of both exercise ECG measurements and prediction equations can substitute for visual analysis performed by cardiologists to predict which patients have severe angiographic coronary artery disease. We performed a retrospective analysis of consecutive patients referred for evaluation of possible or known coronary artery disease who underwent both exercise testing with digital recording of their exercise ECGs and coronary angiography at two university-affiliated Veteran's Affairs medical centers and a Hungarian hospital. There were 2,385 consecutive male patients with complete data who had exercise tests between 1987 and 1997. Measurements included clinical and exercise test data, and visual interpretation of the ECG paper tracings and > 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized ECG measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were only able to correctly classify two or three more patients out of 100 tested than ECG measurements alone. beta-Blockers had no effect on test characteristics while ST depression on the resting ECG decreased specificity. By setting probability limits using the scores from the equations, the population was divided into high-, intermediate-, and low-probability groups. A strategy using further testing in the intermediate group resulted in 86% sensitivity and 85% specificity for identifying patients with severe coronary disease. We conclude that computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist and computerized scores only minimally improved the discriminatory power of the test. However, using these scores in a stratification algorithm allows the nonspecialist physician to improve the discriminatory characteristics of the standard exercise test even when resting ST depression is present. Computerization permitted accurate identification of patients with severe coronary disease who require referral.

Abstract

The type of practitioners who use the standard exercise test is changing. Once a tool of the cardiologist, the standard exercise test is now being performed by internists and other noncardiologists. Because this change could be facilitated by computerization similar to the computerized interpretation programs available for the resting electrocardiograph (ECG), we performed this analysis. A secondary aim was to demonstrate the effects of medication status and resting ECG abnormalities on test diagnostic characteristics because these factors affect utility of the exercise test by the generalist.A retrospective analysis was performed of consecutive patients referred at 2 university-affiliated Veteran's Affairs Medical Centers and a Hungarian Hospital for evaluation of chest pain and possible ischemic heart disease. There were 1384 consecutive male patients without a prior myocardial infarction with complete data who had exercise tests and coronary angiography between 1987 and 1997. Measurements included clinical, exercise test data, and visual interpretation of the ECG recordings as well as more than 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were superior to single ECG measurements. Beta-blockers had no effect on test characteristics, whereas resting ST depression was associated with decreased specificity and increased sensitivity.Computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist; computerized scores that included clinical and exercise test results exhibited the greatest diagnostic power. Applying scores with a computer allows the practicing physician to improve the diagnostic characteristics of the standard exercise test. This approach is successful even when there is resting ST depression, thus lessening the need for more expensive nuclear or imaging studies.

Abstract

Empirical scores, computerized ST-segment measurements, and equations have been proposed as tools for improving the diagnostic performance of the exercise test.To compare the diagnostic utility of these scores, measurements, and equations with that of visual ST-segment measurements in patients with reduced workup bias.Prospective analysis.12 university-affiliated Veterans Affairs Medical Centers.814 consecutive patients who presented with angina pectoris and agreed to undergo both exercise testing and coronary angiography.Digital electrocardiographic recorders and angiographic calipers were used for testing at each site, and test results were sent to core laboratories.Although 25% of patients had previously had testing, workup bias was reduced, as shown by comparison with a pilot study group. This reduction resulted in a sensitivity of 45% and a specificity of 85% for visual analysis. Computerized measurements and visual analysis had similar diagnostic power. Equations incorporating nonelectrocardiographic variables and either visual or computerized ST-segment measurement had similar discrimination and were superior to single ST-segment measurements. These equations correctly classified 5 more patients of every 100 tested (areas under the receiver-operating characteristic curve, 0.80 for equations and 0.68 for visual analysis; P < 0.001) in this population with a 50% prevalence of disease.Standard exercise tests had lower sensitivity but higher specificity in this population with reduced work-up bias than in previous studies. Computerized ST-segment measurements were similar to visual ST-segment measurements made by cardiologists. Considering more than ST-segment measurements can enhance the diagnostic power of the exercise test.

Abstract

To demonstrate that an agreement approach to applying equations on the basis of clinical and exercise test variables is an accurate, self-calibrating, and cost-efficient method for predicting severe coronary artery disease in clinical populations.Retrospective analysis of consecutive patients with complete data from exercise testing and coronary angiography referred for evaluation of possible coronary artery disease. After developing an equation in a training set, this equation and two other equations developed by other investigators were validated in a test set. The study was performed at two university-affiliated Veteran's Affairs medical centers.1080 consecutive men studied between 1985 and 1995 who had coronary angiography within 3 months of the treadmill test. The population was randomly divided into a training set of 701 patients and a test set of 379 patients. Patients with previous coronary artery bypass surgery, valvular heart disease, marked degrees of resting ST depression, and left bundle branch block were excluded.Recording of clinical and exercise test data along with visual interpretation of the electrocardiogram recordings on standardized forms and abstraction of visually interpreted angiographic data from clinical catheterization reports.Simple clinical and exercise test variables improved the standard application of exercise-induced ST criteria for predicting severe coronary artery disease. By setting probability thresholds for severe disease of <20% and >40% for the three prediction equations, the agreement approach divided the test set into three groups: low risk (patients with all three equations predicting <21% probability of severe coronary disease), no agreement, and high risk (all three equations with >39% probability) for severe coronary artery disease. Because the patients in the no agreement group would be sent for further testing and would eventually be correctly classified, the sensitivity of the agreement approach was 89% and the specificity was 96%. The agreement approach appeared to be unaffected by disease prevalence, missing data, variable definitions, or even angiographic criteria.Requiring diagnosis of severe coronary disease to be dependent on agreement between these three equations has made them likely to function in all clinical populations. The agreement approach should be an efficient method for the evaluation of populations with varying prevalence of coronary artery disease, limiting the use of more expensive noninvasive and invasive testing to patients with a higher probability of left main or triple-vessel coronary artery disease. This approach provides a strategy that can be applied by inputting the results of basic clinical assessment into a programmable calculator or a computer to assist the practitioner in deciding when further evaluation is appropriate, thus assuring patients access to subspecialty care.

Abstract

To demonstrate that a consensus approach for combining prediction equations based on clinical and exercise test variables derived from different populations can stratify patients referred for possible coronary artery disease (CAD) into low-, intermediate-, and high-risk groups.Retrospective analysis of consecutive patients with complete data from exercise testing and coronary angiography referred for evaluation of possible CAD. After derivation of a logistic equation in our own training set of patients, this equation, along with two other equations developed independently by other investigators, was validated in a test set. The validation strategy for the consensus approach included the following: (1) calculation of probability scores for each patient using each logistic equation independently; (2) determination of probability thresholds in the training set to divide the patients into three groups-low risk (prevalence CAD <5%), intermediate risk (5 to 70%), and high risk (>70% prevalence of CAD); (3) using agreement among at least two of three of the prediction equations to generate "consensus" for each patient; and (4) application of the consensus approach thresholds to the test set of patients.Two university-affiliated Veteran's Affairs medical centers.We studied 718 consecutive men between 1985 and 1995 who had coronary angiography within 3 months of an exercise treadmill test for suspected CAD. The population was randomly divided into a training set of 429 patients and a test set of 289 patients. Patients with previous myocardial infarction or coronary artery bypass surgery, valvular heart disease, left bundle branch block, or any Q waves present on their resting ECG were excluded from the study.Recording of clinical and exercise test data along with visual interpretation of the ECG recordings on standardized forms and abstraction of visually interpreted angiographic data from clinical catheterization reports.We demonstrated that by using simple clinical and exercise test variables, we could improve on the standard use of ECG criteria during exercise testing for diagnosing CAD. Using the consensus approach divided the test set into populations with low, intermediate, and high risk for CAD. Since the patients in the intermediate group would be sent for further testing and would eventually be correctly classified, the sensitivity of the consensus approach is 94% and the specificity is 92%. The consensus approach controls for varying disease prevalence, missing data, inconsistency in variable definition, and varying angiographic criterion for stenosis severity. The percent of correct diagnoses increased from the 67% for standard exercise ECG analysis and from the 80% for multivariable predictive equations alone to >90% correct diagnoses for the consensus approach.The consensus approach has made population-specific logistic regression equations portable to other populations. Excellent diagnostic characteristics can be obtained using simple data and measurements. The consensus approach is best applied utilizing a programmable calculator or a computer program to simplify the process of calculating the probability of CAD using the three equations.

Abstract

Multivariable analysis of clinical and exercise test variables has the potential to become both a useful tool for assisting in the diagnosis of coronary artery disease and reducing the cost of evaluating patients with suspected coronary disease. Managed care and capitation require that tests such as the exercise test or its replacements, be used only when they can accurately and reliably identify which patients need medications, counseling, or further evaluation or intervention. The replacements for the standard exercise electrocardiogram test require expensive equipment and personnel, and their incremental value is currently being evaluated. Because general practitioners are to function as gatekeepers and decide which patients must be referred to the cardiologist, they will need to use the basic tools they have available (ie, history, physical exam, and the exercise test) in an optimal fashion. However, the discriminating power of the variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. There is a need for further evaluation of these routinely obtained variables to improve the accuracy of prediction algorithms especially in women. Of paramount concern is the need to avoid workup bias by having patients agree to testing before the decision for angiography is made. The portability and reliability of these equations must be shown because access to specialized care must be safeguarded. By reviewing the available studies considering clinical and exercise test variables to predict coronary angiographic findings, we have attempted to provide guidelines and recommendations for a more uniform approach to this endeavor in future investigations. Hopefully, the next generation of multivariable equations will be robust and portable, and empower the clinician to assure the cardiac patient access to appropriate cardiac care.

Abstract

Previous investigators using clinical, hemodynamic, or exercise parameters to predict maximal exercise heart rate (HRmax) have demonstrated age to be the major determinant. Regression coefficients have ranged from -0.3 to -0.6, leaving approximately two thirds of the variance in HRmax unexplained. Because cardiac size and function are directly related to stroke volume and should influence HRmax, we studied 114 male subjects (aged 19 to 73 years) with two-dimensional and M-mode echocardiography who underwent maximal treadmill testing with respiratory gas analysis. Seventy-three were normotensive (diastolic BP < 95 mm Hg) and 41 were hypertensive. As in previous studies, HRmax was inversely related to age (HRmax = 199-0.63[age], r = -0.47, p < 0.001). M-mode left ventricular (LV) diastolic dimension (LVD) added significantly to the explanation of the variance in HRmax (r = -0.57, p < 0.001) (HRmax = 236 - 0.72 [age]-6.8 [LVD]). Thus, the larger the heart, the lower the HRmax. No other echocardiographic measurement or derived parameter added significantly to the explanation of the variance in HRmax. To evaluate the effects of hypertension on HRmax, we studied hypertensives and normotensives separately. Only age was significantly related to HRmax in the normotensives (r = -0.50, p < 0.001). In the hypertensive subjects, however, both age and relative wall thickness (RWT) (which describes LV wall thickness in relation to LV chamber size) were significantly related to HRmax. Age explained 45% of the observed variance in HRmax (r = 0.67, p < 0.001) and RWT added modestly (9%) but significantly to the relationship (HRmax = 173-0.96[age]+94 [RWT], p < 0.001), together explaining 54% of the variance observed in HRmax. Thus, HRmax is inversely related to LVD and patients with larger ventricles achieve lower HRmax. In hypertensives, the amount of LV muscle mass in relation to chamber size is an additional predictor of HRmax. However, despite controlling for age, sex, and cardiovascular disease, and the inclusion of echocardiographic indices of cardiac size and function, a large portion of the variance in HRmax could not be explained. The unexplained variance in HRmax is most likely due to intersubject variability in resting cardiac size, volume, function, and other as yet undefined factors.

Abstract

Controversy persists regarding the mechanism underlying the lactate threshold. It has recently been argued that there is in fact no "threshold" and that blood lactate increases as a continuous function during exercise (Hughson J. Appl. Physiol. 62:1975-1981, 1987). In comparing continuous and threshold models, questions have been raised regarding the ramp rate, data sampling, and the mathematical models employed (Morton J. Appl. Physiol. 67:885-888, 1989). To address some of these concerns, we evaluated 61 subjects (mean age 45 +/- 15), who underwent maximal ramp treadmill tests with the ramp rate individualized such that test duration was approximately 10 min for each subject. The relationship between changes in blood lactate and oxygen uptake were evaluated using a modification of the log-log transformation model described by Beaver (J. Appl. Physiol. 59:1936-1940, 1985) and a continuous exponential plus constant model described by Hughson et al. (J. Appl. Physiol. 62:1975-1981, 1987). Model fitting, using mean squared error (MSE) and coefficient of determination (CD) for each method were as follows: [table: see text] The modified log-log model had a better fit as indicated by the lower MSE and higher CD, suggesting the change in lactate was better described by this model. However, the differences were so slight as to suggest: 1) a meaningful difference does not exist between the two; or 2) these methods may not be capable of detecting a difference, if one exists.

Abstract

Current management of coronary artery disease has taken a very aggressive approach in which cardiac catheterization plays a prominent role in patient evaluation and in which bypass and angioplasty are commonly used for therapy. The number of cardiac catheterizations and procedures, not surprisingly, have grown in tandem because angiography provides anatomic information that becomes the substrate for justifying interventions. Bypass surgery has been shown to confer a survival benefit compared with medical therapy in patients with multiple-vessel disease and left ventricular dysfunction, but it also is still used in other patient populations with equivocal indications. Comparison studies of percutaneous transluminal coronary angioplasty with medical management have indicated a slight advantage with percutaneous transluminal coronary angioplasty in limiting symptoms, but no evidence yet supports its survival benefit. Angioplasty, however, has become much more common in the last decade, particularly as the initial revascularization technique. Because cardiac catheterization is frequently the nodal branch point between invasive and noninvasive (i.e., medical) management, its application should be limited to high-risk candidates who would receive a survival benefit from these procedures or to those with intractable symptoms. Those who propose that catheterization is the best method for risk stratification argue that noninvasive testing requires physiologically significant disease and that morbid or fatal events can occur with rapid progression of minimal disease. From the studies reviewed, however, the extent of coronary angiographic disease is not clearly predictive of future cardiovascular events. Although some studies found the number of diseased vessels to be independent prognostic variables, most found that it did not add any additional prognostic information beyond that provided from noninvasive testing. Furthermore, there has been an argument that silent ischemia puts patients at higher risk of sudden death or infarction, and these patients need to be catheterized. However, numerous studies have shown that this concern is exaggerated. The studies reviewed found that except for patients with diabetes, those with "silent" or painless exercise-induced ST depression do not have a worse prognosis than those with symptomatic ST depression when cardiovascular death, sudden death, or acute myocardial infarction are considered Clinical and exercise test variables have been underused in estimating prognosis. Specifically, they are rarely used systematically to stratify patients into low-risk groups who do not need catheterization and high-risk groups who should undergo angiography because of possible lesions amenable to bypass or angioplasty.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract

A growing number of physicians are performing exercise tests in their offices for the purposes of diagnosing cardiopulmonary disease and assessing exercise capacity in patients with heart disease. Methodology of testing is important in making the most effective use of the information gathered from the test. Selecting an approach that fits the objectives of the test and the individual being tested is essential for accurate and reproducible results. This article discusses the various exercise protocols and equipment used in exercise testing.

Abstract

Recent investigations suggested that clinical exercise testing can be optimized by individualizing the protocol, depending on the purpose of the test and the subject tested. This requires some knowledge of a patient's exercise capacity before beginning the test. The accuracy of a simple physical activity questionnaire and readily available clinical data in predicting subsequent treadmill performance was examined. A brief, self-administered questionnaire (VSAQ) was developed for veterans who were referred to exercise testing for clinical reasons. The VSAQ was designed to determine which specific daily activities were associated with symptoms of cardiovascular disease (fatigue, chest pain and shortness of breath). Two hundred twelve consecutive patients (mean age 62 +/- 8 years) referred for maximal exercise testing were studied. Clinical and demographic variables were added to VSAQ responses in a stepwise regression model to determine their ability to predict treadmill performance. Only metabolic equivalents by VSAQ, and age were significant predictors of treadmill performance; these 2 variables yielded R = 0.82 (SEE 1.43; p < 0.001), and explained 67% of the variance in exercise capacity. The regression equation reflecting the relation between age, VSAQ and exercise capacity was: achieved metabolic equivalents = 4.7 + 0.97 (VSAQ) - 0.06 (age). Using this equation, a nomogram was developed. Incorporating the VSAQ with the nomogram requires only a few minutes, and yields a reasonably accurate estimate of a patient's exercise capacity. Although the present equation is population-specific, a similar approach in different populations may be useful for individualizing protocols for clinical exercise testing.

Abstract

Treadmill and clinical data were gathered prospectively on consecutive patients who underwent exercise testing for evaluation for coronary artery disease in a 1,200 bed Veterans Affairs Medical Center. From 3,609 men referred for exercise testing from 1984 to 1990, 3,134 patients remained after excluding those with significant valvular heart disease and those with prior coronary artery bypass surgery. Of these, 588 were selected for clinical reasons to undergo cardiac catheterization within 3 months of evaluation leaving 2,546 who were not selected. Over 3 years, there were 158 cardiovascular deaths, 99 nonfatal myocardial infarcts and 183 patients who underwent coronary artery bypass surgery. In the total population, the Cox proportional-hazards model demonstrated the following characteristics to be statistically significant independent predictors of time until cardiovascular death: a history of congestive heart failure and/or taking digoxin, exercise-induced ST depression, the change in systolic blood pressure during exercise, and exercise capacity in METs. Using the Cox model coefficients to weight the variables, a simple score (the Veterans Affairs Prognostic Score) was constructed based on these items. Average annual cardiovascular mortality was plotted against the score enabling its estimation for any given patient. In the subgroup selected for cardiac catheterization (n = 588), the mean score was greater, consistent with a poorer prognosis, compared with the total population; 53% (n = 312) had a score < -2 associated with an annual mortality < 2%. Thus, in over half of the patients selected for catheterization, the catheterization was unnecessary if performed to lessen their chance of cardiovascular death, since no intervention could improve their prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract

Forty-two patients with angiographically documented left main coronary artery (LM) disease (luminal occlusion > or = 50%) and 30 patients with left main equivalent (LMEQ) disease (> or = 70% luminal occlusion of both the proximal left anterior descending artery and proximal left circumflex artery) were studied to determine the role of right coronary artery (RCA) involvement on exercise test responses and survival. Significant (> or = 70%) RCA stenosis was present in 30 (72%) of the 42 LM patients and 16 (53%) of the 30 LMEQ patients. No significant differences were observed between LM and LMEQ patients in any clinical or exercise variables or survival. Thus both groups were combined for analysis of the influence of RCA involvement (i.e., LM/LMEQ with RCA versus LM/LMEQ without RCA disease). Greater ischemic responses were observed in the LM/LMEQ group with significant stenosis of the RCA. The presence of RCA stenosis was associated with significantly greater horizontal or downsloping ST-segment depression during exercise (2.4 +/- 1.2 mm vs 1.3 +/- 1.4 mm; p < 0.001), and prolonged recovery time until normalization of the ST segment (3.2 +/- 1.4 min vs 2.0 +/- 1.9 min; p < 0.01). The LM/LMEQ without RCA disease group behaved like the subgroup with two-vessel disease, and responses of the LM/LMEQ group with RCA disease were similar to the group with three-vessel disease. The annual survival in LM/LMEQ with RCA disease was worse than that in LM/LMEQ without RCA disease (average annual mortality rates = 7.5% vs 1.0%, respectively; p = 0.05). Infarct-free survival in LM/LMEQ with RCA disease was also lower than that in LM/LMEQ without RCA disease. Thus although patients with LM and LMEQ were similar in terms of survival and exercise responses, the presence of RCA stenosis was associated with significantly greater ST-segment depression, a prolonged recovery time until normalization of the ST segment, a fivefold increase in the death rate, and higher morbidity from myocardial infarction over a 5-year period of follow-up. Involvement of the RCA should be considered when making decisions concerning medical-surgical management of patients with severe coronary artery disease.

Abstract

The objective of this study was to determine whether coronary angiographic findings and survival could be predicted using standard clinical and exercise-test data.Five hundred and ninety-five men who had undergone both exercise treadmill testing and cardiac catheterization were followed for up to 5 years. Left main (LM) disease (> or = 50% stenosis) was present in 42 patients, whereas 30 patients had LM equivalent disease (> or = 70% stenosis of both the proximal left anterior descending and circumflex coronary artery disease (n = 152), one-vessel disease (n = 186), two-vessel disease (n = 118), three-vessel disease (n = 67), LM or LM equivalent disease without significant (> or = 70%) right coronary artery involvement (n = 26), and LM or LM equivalent disease with right coronary artery involvement (n = 46).ST-segment depression was more marked, whereas ejection fraction, maximal heart rate, maximal systolic blood pressure, and exercise capacity were lower in each group as disease severity worsened. Using Kaplan-Meier analysis, the subgroup with the poorest survival was found to be those with LM or LM equivalent disease with right coronary artery disease, and the next worse was the three-vessel disease group, in which survival was poorer than in all other subgroups (P < 0.01). Stepwise regression analysis revealed that the most powerful predictor for coronary artery disease severity was exercise-induced ST depression (P < 0.001), but it predicted survival poorly. History of congestive heart failure, low ejection fraction (50% or lower), and poor exercise capacity (5 metabolic equivalents or less) emerged as strong predictors of survival using stepwise Cox regression analysis (P < 0.001).Exercise-induced ST depression predicted the severity of angiographic disease but not survival, whereas the strongest predictors of survival were history of congestive heart failure, low ejection fraction, and poor exercise capacity.

Abstract

To quantitate changes in gas exchange variables that occur after administration of sublingual nitroglycerin in patients with stable angina pectoris, a randomized double-blind 2-period crossover study was performed with continuous expired gas exchange analysis and progressive exercise using individualized ramp treadmill protocols. Significant reductions in minute ventilation and respiratory rate were observed at 5 minutes of exercise during nitroglycerin therapy. Gas exchange variables i.e., minute ventilation, carbon dioxide production and oxygen uptake were significantly increased at the onset of angina after nitroglycerin administration. When techniques for optimizing the assessment of cardiopulmonary function were used, significant improvements in gas exchange variables were demonstrated in stable angina pectoris after administration of sublingual nitroglycerin.

Abstract

The evidence suggesting that regular exercise can help to prevent coronary artery disease is overwhelming. While some studies have suggested that exercise will not provide health benefits, our inactive population needs to pay heed to the substantial data presented by the many international health organisations suggesting the opposite. The American Heart Association Medical/Scientific Statement on Exercise emphasised the large role regular aerobic physical activity plays in the prevention of cardiovascular disease. Several human studies have also demonstrated the positive effects of long term exercise on the human heart. For example, it has been shown that a consistent exercise programme can lessen the impact of atherosclerotic plaques through increasing coronary artery diameter. Echocardiography studies on a training group of competitive swimmers have shown that exercise training can induce rapid changes in left ventricular dimensions and mass, which can ultimately lead to an increased stroke volume and increased maximal oxygen consumption. Studies on sedentary individuals have also demonstrated an increase in maximal oxygen uptake with a regular endurance exercise programme. In addition to these health benefits, habitual dynamic exercise can also decrease the likelihood of a cardiac event. Others have demonstrated a 50% lower incidence of coronary events in those individuals maintaining rigorous activity 2 days a week. With the preponderance of evidence revealing the health benefits of habitual exercise, it is striking to learn that more than 50% of the US population exercises for less than 20 minutes, 3 days a week. The widespread nature of this sedentary lifestyle makes inactivity an attributable fraction of the total risk factors associated with cardiac disease. The amount of exercise needed to reduce the risk of coronary artery disease is a minimum aerobic workout of 30 minutes, 4 to 5 times a week, such as a vigorous walk. Comprehensive programmes promoting exercise training should be implemented at a level appropriate to an individual's capacity and need.

NOMOGRAM BASED ON METABOLIC EQUIVALENTS AND AGE FOR ASSESSING AEROBIC EXERCISE CAPACITY IN MENJOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGYMORRIS, C. K., Myers, J., Froelicher, V. F., Kawaguchi, T., Ueshima, K., HIDEG, A.1993; 22 (1): 175-182

Abstract

The goal of this study was to create a nomogram, based on maximal exercise capacity (in metabolic equivalents [METs]) and age, for assessing a patient's ability to perform dynamic exercise to quantify the level of physical disability or relative capacity for physical activity.Providing an estimation of exercise capacity relative to age is clinically useful. Such an estimate can be derived from measured or estimated maximal oxygen uptake (in METs) from treadmill exercise testing and age. It is an effective means of communicating to patients their cardiopulmonary status, encouraging improvement in exercise capacity and quantifying disability.Exercise test results of 1,388 male patients (mean age 57 years, range 21 to 89) free of apparent heart disease who were referred for exercise testing for clinical reasons were retrospectively reviewed. This referral group as well as subgroups of active (n = 346) and sedentary (n = 253) patients were analyzed to determine norms for age and for age by decades for exercise test responses, including METs, maximal heart rate and maximal systolic blood pressure. Regression equations were calculated from this information, and a nomogram for calculating degree of exercise capacity from age and MET level achieved by a patient was created. A similar analysis was performed in a separate group of 244 apparently healthy, normal male volunteers (mean age 45 +/- 14 years, range 18 to 72) who underwent exercise testing with direct measurement of expired gases.Equations for predicted METs for age were derived for the entire clinical referral group (METs = 18.0-0.15[Age]) and for the subgroups of active (METs = 18.7-0.15[Age]) and sedentary (METs = 16.6-0.16[Age]) patients. All results achieved statistical significance, with p values < 0.001. In the volunteer group of normal men who performed exercise testing with ventilatory gas exchange, the decline in maximal heart rate and METs with age was not as steep as in the referral group. Although the normal group confirmed nomograms published previously among similar subjects, the equations derived from the patients differed from those previously reported; in contrast to previous studies using healthy volunteers, the equations and nomograms for the referral group are more appropriate for patients typically referred for testing in a hospital or office-based internal medicine practice.Norms for METs based on age are presented as well as population-specific nomograms that enable physicians to assess patients' exercise capacity relative to their age group.

Abstract

The objective of the study was to optimize the accuracy of the exercise test for predicting the presence of significant angiographic coronary artery disease. A retrospective analysis of stored digital exercise electrocardiographic data on 147 men who had undergone exercise testing and cardiac catheterization was performed. With significant coronary artery disease defined as > or = 70% stenosis, 95 patients had one or more vessel(s) diseased. None were receiving digoxin, had a myocardial infarction or previous coronary artery bypass graft, or exhibited left bundle branch block, left ventricular hypertrophy, Q waves, or ST depression on their resting electrocardiogram. Analysis was performed using the authors' averaging and measurement software at rest and at each 30 seconds throughout the exercise and recovery in leads II, V2, and V5. Discriminant function analysis was used to analyze pretest variables, as well as hemodynamic and electrocardiographic changes and symptoms during exercise. A discriminant function score was developed and compared to other treadmill scores. The setting was a 1,000 bed Veterans Affairs Medical Center (Long Beach, CA). Discriminant function analysis chose age, smoking status, presenting chest pain characteristics, and lead V5 ST slope in recovery to have independent power for separating those with and without coronary artery disease. A discriminant function score using these four variables was used to form a receiver operating characteristics curve (and derive receiver operating characteristics curve areas) for comparison to other exercise test methods and scores: (discriminant function score = .81; slope 3.5 minutes into recovery in lead V5 = .73; traditional ST amplitude method = .72; ST60/HR index (amplitude of ST depression 60 ms after the J point/delta heart rate) = .66; traditional ST amplitude/HR index (traditional method/delta heart rate) = .75; Hollenberg score = .68; Hollenberg areas only = .66; and ST integral = .66. Receiver operating characteristics curve analysis revealed a trend for the discriminant function score to be superior to all other measurements and scores. Recovery ST slope in lead V5 performed as well as or better than all other electrocardiographic criteria or treadmill scores except for the authors' discriminant function score.

Abstract

The objective of this report is the development of a population-specific prediction rule based on clinical and exercise test data that would estimate the risk of cardiovascular death in patients selected for cardiac catheterization. Prospective data and follow-up information were obtained from patients who underwent cardiac catheterization soon after clinical assessment and exercise testing. Males (n = 588) referred for evaluation of coronary heart disease from 1984 to 1990 were selected after exclusion of patients with significant valvular heart disease and patients with prior cardiac surgery. Half had a prior myocardial infarction and half complained of typical angina pectoris. All patients performed a treadmill test and were selected for clinical reasons to undergo coronary angiography within 3 months. Over a mean follow-up period of 2.5 years (+/- 1.4 years), there were 39 cardiovascular deaths and 45 nonfatal myocardial infarctions. The Cox proportional hazards model demonstrated the following characteristics to be statistically significant independent predictors of time until cardiovascular death: history of congestive heart failure (hazards ratio of 4), ST depression on the resting ECG (hazards ratio of 3), and a drop in systolic blood pressure below the resting value during exercise (hazards ratio of 5). Exercise-induced ST depression was not associated with either death or nonfatal myocardial infarction. A simple score based on one item of clinical information (history of congestive heart failure), a resting ECG finding (ST depression), and an exercise test response (exertional hypotension) stratified our patients for 4 years after testing from 75% with a low risk (annual cardiac mortality rate of 1%), 17% with a moderate risk (annual mortality rate of 7%), and 1% with a high risk (annual cardiac mortality rate of 12%, with a hazards ratio of 20 and 95% confidence interval from 6 to 70X). It was concluded that the variables available from the usual noninvasive workup of patients with known or suspected coronary artery disease enable prediction of risk of cardiovascular death. Three quarters of those usually undergoing cardiac catheterization can be identified by simple noninvasive variables as being at such low risk that invasive intervention is unlikely to improve prognosis.

Abstract

To evaluate the response of patients with chronic atrial fibrillation (AF) to exercise, 79 male patients (mean age 64 +/- 1 years) with AF underwent resting two-dimensional and M-mode echocardiography and symptom-limited treadmill testing with ventilatory gas exchange analysis. Patients were classified by underlying disease into five subgroups: no underlying disease (LONE: n = 17), hypertension (HT: n = 11), ischemic heart disease (n = 13), cardiomyopathy or history of congestive heart failure (CHF: n = 26), and valvular disease (n = 12). A higher maximal heart rate than expected for age was observed (175 vs 157 beats/min), which was most notable in the LONE and HT subgroups. Maximal oxygen uptake (VO2 max) was lower than expected for age in all groups. Patients with CHF had a lower resting ejection fraction than all other patients (p < 0.001), a lower VO2 max, and a lower maximal heart rate than LONE and HT patients (p < 0.001). Stepwise regression analysis demonstrated that echocardiographic measurements at rest were poor predictors of VO2 max and VO2 at the ventilatory threshold. Among clinical, morphologic, and exercise variables, maximal systolic blood pressure accounted for the greatest variance in exercise capacity, but it explained only 35%. In patients with AF the higher than predicted maximal heart rates may be a compensatory mechanism for maintaining exercise capacity after the loss of normal atrial function. However, even in the absence of underlying disease, it does not appear to compensate fully for a compromised exercise capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract

Although important strides have been made in related procedures, exercise ECG remains an invaluable tool in the initial assessment of coronary disease and yields a great deal of prognostic information. Access to limited health care resources often hinges on its outcome. Proper methodology is critical to patient safety and to obtain accurate results. The importance of patient education, physician interaction with the patient, skin preparation, and criteria for exclusion and termination cannot be overemphasized. A brief physical examination and 12-lead ECG in both the supine and standing positions should precede exercise testing. Few studies have correctly evaluated the relative yield or sensitivity and specificity of different electrode placements for exercise-induced shifts in the ST segment. The use of other leads in addition to V5 increases test sensitivity, but the specificity may be reduced. ST-segment changes isolated to the inferior leads are frequently false-positive responses. Vectorcardiographic and body surface mapping lead systems do not appear to offer any advantage over simpler approaches for clinical purposes. Changes caused by exercise electrode placement can be kept to a minimum by placing arm electrodes on the shoulders, off of the chest. The exercise protocol should be progressive, with even increments in speed and grade whenever possible. Smaller, even, and more frequent work increments are preferable to larger, uneven, and less frequent increases, because the former yield a more accurate estimation of exercise capacity. The value of individualizing the exercise protocol rather than using the same protocol for every patient has recently been emphasized by many investigators. The optimal test duration is from 8 to 12 minutes, and the protocol workloads should be adjusted to permit this duration. Because ramp testing uses small increments, it permits a more accurate estimation of exercise capacity and can be individualized for every patient to yield a targeted test duration. Target heart rates based on age should not be used because the relationship between maximal heart rate and age is poor and varies greatly. The Borg scale is a useful means of quantifying an individual's effort. Exercise capacity should not be reported in total time but rather as the VO2 or MET equivalent of the workload achieved. This permits comparison of the results between many different exercise testing protocols. Gas-exchange techniques can greatly supplement exercise testing by adding precision and reproducibility and increase the yield of information concerning cardiopulmonary function. Estimating work from treadmill or cycle ergometer workload introduces a great deal of error and variability.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract

To develop prediction rules from clinical and exercise test data identifying patients at high and low risk for cardiovascular events among a group of male veterans.Prognostic study with prospective gathering of data and routine follow-up of consecutive patients referred for exercise testing. Patients only underwent noninvasive evaluation for coronary artery disease. No validation cohort is yet available.A 1200-bed Veterans Affairs Medical Center.Of 3609 men referred for exercise testing between 1984 and 1990, 2546 patients remained evaluable after exclusion of those who underwent subsequent cardiac catheterization, those with significant valvular heart disease, and those who had previous coronary artery bypass surgery.Evaluation included recording of clinical data on a standardized form and a standard treadmill test followed by assessment of cardiovascular events.During a mean follow-up period (+/- SD) of 2.75 (+/- 18) years, 119 cardiovascular deaths and 44 nonfatal myocardial infarctions occurred in 2546 patients. The Cox proportional hazards model showed the following characteristics to be statistically independent predictors of time until cardiovascular death: history of congestive heart failure or digoxin use, exercise-induced ST depression, change in systolic blood pressure during exercise, and exercise capacity. Using a simple score based on one item of clinical information (history of congestive heart failure or digoxin use) and three exercise test responses (ST depression, exercise capacity, and change in systolic blood pressure), 77% of patients were categorized as low risk (annual cardiac mortality rate, less than 2%), 18% as moderate risk (annual cardiac mortality rate, 7%), and 6% as high risk (annual cardiac mortality rate, 15%; hazard ratio, 10; 95% confidence interval, 6 to 17). This model has not yet been validated.Variables available from the usual non-invasive work-up of patients with known or suspected coronary artery disease can be used to predict future risk for cardiovascular death.

Abstract

To determine which computer ST criteria are superior for predicting patterns and severity of coronary artery disease during exercise testing, 230 male veterans were studied who had both coronary angiography and a treadmill exercise test. Significant (p < or = 0.05) differences in computer-scored ST criteria were observed among patients with progressively increasing disease severity. Three-vessel/left main disease produced responses significantly different from 1- and 2-vessel disease or those with < 70% occlusion. Discriminant function analysis revealed that horizontal or downsloping ST depression measured at the J junction during exercise or recovery, or both, was the most powerful predictor of severe disease. With use of a cut point of 0.075 mV ST depression, horizontal or downsloping ST depression alone yielded a sensitivity of 50% (95% confidence interval = 35 to 65%) and specificity of 71% for prediction of severe disease; the only additional variable that added significantly to the prediction was exercise capacity, which improved sensitivity to 57% (95% confidence interval = 41 to 72%) with no change in specificity. Measurements of ST amplitude at the J junction and at 60 ms after the J point without slope considered and other scores, including the Treadmill Exercise Score, ST Integral, and ST/heart rate index, had a lower but comparable predictive accuracy when compared with horizontal or downsloping ST depression. Prediction of coronary artery disease severity can be achieved using computerized electrocardiographic measurements obtained during exercise testing. The most powerful marker for severe coronary artery disease is the amount of horizontal or downsloping ST-segment depression during exercise or recovery, or both, a measurement that stimulates the traditional visual approach.

Abstract

Mechanisms that have been suggested to underlie the abnormal ventilatory response to exercise in patients with chronic congestive heart failure (CHF) include high pulmonary pressures, ventilation-perfusion mismatching, early metabolic acidosis, and abnormal respiratory control. To evaluate the role that ventilation and gas exchange play in limiting exercise capacity in patients with CHF, data from 33 patients with CHF and 34 normal subjects of similar age who underwent maximal exercise testing were analyzed. Maximal oxygen uptake was higher among normal subjects (31.7 +/- 6 ml/kg/min) than among patients with CHF (17.7 +/- 4 ml/kg/min; p less than 0.001). The ventilatory equivalent for oxygen, expressed as a percentage of maximal oxygen uptake, was 25% to 35% higher among patients with CHF compared with normal subjects throughout exercise (p less than 0.01). A steeper component effect of ventilation on maximal oxygen uptake was observed among normal subjects compared with patients with CHF, which suggests that a significant portion of ventilation in CHF is wasted. Maximal oxygen uptake was inversely related to the ratio of maximal estimated ventilatory dead space to maximal tidal volume (VD/VT) in both groups (r = -0.73, p less than 0.001). Any given oxygen uptake at high levels of exercise among patients with CHF was accompanied by a higher VD/VT, lower tidal volume, and higher respiratory rate compared with normal subjects (p less than 0.01). Relative hyperventilation in patients with CHF started at the beginning of exercise and was observed both below and above the ventilatory threshold, which suggests that the excess ventilation was not directly related to earlier than normal metabolic acidosis. Thus abnormal ventilatory mechanisms contribute to exercise intolerance in CHF, and excess ventilation is associated with both a higher physiologic dead space and an abnormal breathing pattern. The high dead space is most likely due to ventilation-perfusion mismatching in the lungs, which is related to poor cardiac output, and the abnormal breathing pattern appears to be an effort to reduce the elevated work of breathing that is caused by high pulmonary pressures and poor lung compliance.

Abstract

In a Veterans Affairs Medical Center, we studied 607 male patients to determine whether patterns and severity of coronary artery disease could be predicted by means of standard clinical and exercise test data. We found significant differences in clinical, hemodynamic, and electrocardiographic measurements among patients with progressively increasing disease severity determined by angiography. Left main disease produced responses significantly different from those of three-vessel disease only when accompanied by a 70% or greater narrowing of the right coronary artery. Discriminant function analysis revealed that the maximum amount of horizontal or downsloping ST depression in exercise and/or recovery was the most powerful predictor of disease severity, with 2-mm ST depression yielding a sensitivity of 55% and a specificity of 80% for prediction of severe coronary artery disease (three-vessel disease plus left main disease). Patients with increasingly severe disease also demonstrated a greater frequency of abnormal hemodynamic responses to exercise.

Abstract

The many different approaches to exercise testing have hindered the consistent interpretation of hemodynamic, electrocardiographic, and ventilatory gas exchange responses. One of the most influential approaches is the choice of the exercise protocol. Recent data suggest that the protocol can have an important impact on test sensitivity, the reason for test termination, the ST/HR slope calculation, the interpretation of gas exchange responses, and the accuracy with which oxygen uptake is predicted from work rate. Recent recommendations for optimizing the test have focused on the test duration, reducing the increments in work rate, and individualizing the test relative to the purpose of the test and the subject tested. We describe a treadmill test which considers these recommendations for optimizing exercise testing.

Abstract

Various modifications and refinements have been proposed to improve the diagnostic accuracy of standard ST-segment criteria for identifying coronary artery disease using exercise testing. To ascertain if the treadmill exercise score (TES), the ST integral, or the ST/HR index are significantly better markers for coronary disease the standard ST analysis, measured visually or by computer, a retrospective study of 173 male patients was performed. Exclusions were clinical or electrocardiographic evidence of prior myocardial infarction, left ventricular hypertrophy, left bundle branch block, or resting ST segment depression on their baseline electrocardiogram, digitalis, previous revascularization procedure or any significant valvular or congenital heart disease. Ninety-six patients (55.5%) had at least one epicardial coronary stenosis (more than 70% diameter stenosis). Cutpoints were chosen for each method, that maximized their best combination of sensitivity and specificity. There were no statistically significant differences between any of the five methods (TES, ST integral, ST/HR index, standard and computer ST analysis) for identifying any coronary disease. Conclusion: careful visual or ST-segment analysis continues to be the simplest as well most effective marker for coronary disease during exercise testing.

Abstract

Multiple lead systems are shown to have a higher sensitivity than that of single leads for detecting coronary artery disease (CAD) during exercise testing, but the value of ST-segment depression isolated to the inferior leads is questionable. To ascertain the diagnostic accuracy of inferior limb lead II compared with that of precordial lead V5, a retrospective analysis of 173 men was performed (108 in a training population and 65 in a validation cohort). All patients had a standard exercise test and underwent diagnostic coronary angiography within 15 days of the exercise test (range 1 to 65). Sixty-three patients had greater than or equal to 1 coronary stenoses greater than or equal to 70%, or left main lesion greater than or equal to 50%, whereas 45 patients in the training population did not. Exclusion criteria were female sex, left ventricular hypertrophy, left bundle branch block or resting ST-segment depression on the baseline electrocardiogram, previous myocardial infarction or revascularization procedures, and any significant valvular or congenital heart disease. Lead V5 had a better combination of sensitivity (65%) and specificity (84%) (chi-square = 24.11; p less than 0.001) than that of lead II (sensitivity 71%, specificity 44%) (chi-square = 2.25; p = 0.13) at a single cut point, and this improved specificity was substantial (95% confidence interval for observed difference 22 to 58%). Receiver-operating characteristic curve analysis also revealed that lead V5 (area = 0.759) was markedly superior to lead II (area = 0.582) over multiple cut points (z = 3.032; 2p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract

This study tested the hypothesis that discriminant function analysis of clinical and exercise-test variables including computerized ST measurements could improve the prediction of severe coronary artery disease. Secondary objectives were to demonstrate the effect of digoxin and/or resting electrocardiographic (ECG) abnormalities, and to evaluate the relative importance of ST measurements made during the recovery phase and in the three lead group areas. The design was a retrospective analysis of data collected during exercise testing and coronary angiography. The ECG data were gathered and stored in digital format on optical discs and all ST measurements were made off-line using the authors' own software. Univariate and multivariate analytic methods were used to analyze all pretest characteristics as well as hemodynamic and computerized ECG responses to exercise. A 1,000-bed Veterans Affairs Medical Center served as the setting. The study included 446 male veterans who underwent a sign or symptom limited treadmill exercise test and coronary angiography. Analysis was also performed on a subset of this population formed by excluding patients receiving digoxin or with resting ECGs exhibiting left ventricular hypertrophy or ST depression (n = 328). In the total study population, the authors derived a treadmill score using discriminant function analysis. This score included: (1) the time-slope area in lead V5 during recovery; (2) delta heart rate; (3) angina pectoris during the exercise test; and (4) presence of diagnostic Q waves on the resting ECG. This score was effective in predicting triple vessel/left main disease and outperformed exercise-induced ST depression for predicting severe coronary artery disease. After exclusion of patients with ECGs exhibiting left ventricular hypertrophy or resting ST depression and patients receiving digoxin, discriminant function analysis chose: (1) the time-slope area in lead V5 during recovery and (2) delta heart rate. Exclusion of these patients resulted in a nonsignificant decrease in specificity of all ST criteria. ST-segment amplitude or slope in lead V5 at 3.5 minutes in recovery clearly outperformed the maximal exercise measurements in both groups. Summing the depressions or selecting the most depression in the three areas (ie, lateral-V5, inferior-II, anterior-V2) did not improve test performance. Leads other than V5 did not contain significant diagnostic information. A quantitative approach to exercise testing using discriminant function analysis enhanced the tests' performance for predicting severe coronary disease. The inclusion of patients taking digoxin or with resting ECG abnormalities nonsignificantly decreases the specificity of all ST criteria.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract

The presence or absence of baseline diagnostic Q waves has been believed to compromise the accuracy of standard exercise electrocardiography in identifying severe coronary artery disease (three-vessel and/or left main disease); therefore, a retrospective analysis was performed using a personal computer data base of exercise test responses and cardiac catheterization results to evaluate this premise, and follow-up was performed to observe how Q waves and/or severe coronary disease impacted on survival.Two hundred fifty-three male patients who had survived a myocardial infarction were studied. Patients on digitalis, those with left bundle branch block or left ventricular hypertrophy on their baseline electrocardiogram, those with previous revascularization procedures, and those with significant valvular or congenital heart disease were excluded. All patients performed either a low-level predischarge or a sign/symptom limited exercise test and underwent diagnostic coronary angiography within 32 days of each test (range, 0-90 days). Long-term follow-up on patients was performed for an average of 45 months (+/- 17 months). Group NQMI comprised 103 post-myocardial infarction patients lacking Q waves at the time of exercise testing and group QMI comprised 150 patients who developed Q waves with their myocardial infarction. The cut points of greater than or equal to 1 mm (chi 2 = 14.39, p less than 0.001) and greater than or equal to 2 mm (chi 2 = 26.11, p less than 0.001) of exercise-induced ST segment depression were reliable markers of severe coronary disease in Q wave infarct survivors. This was also true for non-Q wave infarct survivors as greater than or equal to 1 mm (chi 2 = 6.02, p = 0.01) and greater than or equal to 2 mm (chi 2 = 4.37, p = 0.04) of ST segment depression were reliable markers of severe coronary disease. Receiver operating characteristic curve analysis revealed that exercise-induced ST segment depression had discriminating power for the identification of severe coronary artery disease in both the Q wave myocardial infarction patients (area = 0.735, z = 4.47, p less than 0.001) and the non-Q wave infarct patients (area = 0.700, z = 3.20, p less than 0.001). After 4.4 years of cumulative follow-up, patients with severe coronary disease had an infarct-free survival rate of 72% (95%, CI, 50.0-86.0%), whereas those without severe disease had an 86% (95% CI, 76.5-91.5%) infarct-free survival rate (Cox chi 2 = 4.00, p = 0.045). Non-Q wave patients had an infarct-free survival rate of 81% (95% CI, 66.0-89.5%), whereas those with Q waves had an infarct-free survival rate of 85% (95% CI, 73.9-91.3%) (Cox chi 2 = 0.0005, p = NS).The presence or absence of diagnostic Q waves has no significant effect on the ability of the exercise electrocardiogram to identify severe coronary artery disease in survivors of myocardial infarction. Long-term infarct-free survival of patients with myocardial infarction is more related to the presence of severe coronary disease rather than if they suffered a non-Q wave or Q wave infarction.

Abstract

Resting ST segment depression has been identified as a marker for adverse cardiac events in patients with and without known coronary artery disease. To correlate this with exercise testing, coronary angiography, and how it impacts on long-term prognosis, a retrospective study was performed on 476 patients, of whom 223 had no clinical or electrocardiographic evidence of prior myocardial infarction while 253 were survivors of an infarction. All patients performed a standard exercise test and underwent diagnostic coronary angiography within an average of 32 days of their exercise test (range 0 to 90 days). Exclusions were women, those with left bundle branch block, left ventricular hypertrophy, use of digoxin, previous revascularization procedures, or significant valvular or congenital heart disease. Long-term follow-up was carried out for an average of 45 months (+/- 17). Of the patients without prior infarction, 23 (10%) had persistent resting ST segment depression, and of those with a prior history of infarction, 37 (15%) also had resting ST segment depression. Patients with resting ST segment depression and no prior myocardial infarction had a higher prevalence of severe coronary disease (three-vessel and/or left main) (30%) than those without resting ST segment depression (16%) (95% confidence interval [CI] for observed difference -5.0% to 33.9%, p = 0.12). The criterion of greater than or equal to 2 mm of additional exercise-induced ST segment depression was a particularly useful marker in these patients for the diagnosis of any coronary disease (likelihood ratio 3.35, 95% CI 0.56 to 19.93, p = 0.06). Patients with resting ST segment depression and a prior myocardial infarction had a 2.5 times higher prevalence of severe coronary artery disease compared with patients without resting ST segment depression (43% versus 17% prevalence, respectively, 95% CI for observed difference 9.38% to 42.8%, p less than 0.001) and also had larger left ventricles postinfarction (left ventricular end-diastolic volume index 102 ml/m2 compared with 96 ml/m2, p less than 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract

While there is still much debate in the literature regarding the specific MET levels at which there are differences in survival, the following points have become clear with the growing body of reports in the literature. Exercise capacity seems to be an independent predictor of mortality, and when it is combined with other clinical, exercise, or angiographic data, it becomes very powerful in this regard. This relates to both overall mortality and to that from cardiovascular disease. There is still a need for the establishment of mortality data related to MET levels adjusted for age and activity status. A low exercise capacity of less than 6 METs indicates a higher mortality group, probably regardless of the underlying extent of coronary disease or left ventricular function. Analysis of the CASS data has indicated that these patients benefit from coronary artery bypass surgery with respect to survival. An exercise capacity of greater than 10 METs designates an excellent survival group, again despite the extent of coronary artery disease or left ventricular function. If 10 METs truly exerts a "protective effect" that obviates any survival benefit from coronary artery bypass surgery, this has enormous implications for cost containment and medical care. It is nonetheless important to remember that this level of exercise capacity does not imply the absence of either coronary disease or triple-vessel coronary disease. Exercise capacity is related to more than just cardiovascular fitness and integrity. It is dependent upon a combination of other physiologic components as well, including pulmonary function, health status of other organ systems, nitrogen balance, nutritional status, medications, orthopedic limitations, and others.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract

The diagnostic value of exercise-induced ST segment depression is considered to be decreased in patients receiving beta-blockers. One approach to improving predictive accuracy has been to use the ratio of maximal change in exercise-induced ST segment depression to the corresponding maximal change in heart rate (delta ST/HR index). The present study compared these two ECG methods. The records of exercise tests performed on 3047 male veterans were screened to exclude patients with prior revascularization procedures or myocardial infarction, those receiving digoxin, and those with certain resting ECG abnormalities; the use of beta-blocker drugs at the time of testing was also noted. All exercise tests were sign/symptom limited. Significant angiographic coronary disease was defined as greater than or equal to 75% reduction in luminal diameter of at least one coronary artery. Disease severity was evaluated in an expanded study group that included patients with prior myocardial infarction. Mean maximal heart rate was 21 beats.min-1 lower for those receiving beta-blockers (p less than 0.05), but there was no difference in mean metabolic equivalent (MET) level achieved. The diagnostic accuracy of an abnormal test result for determination of the presence or absence of coronary artery disease was not significantly different in the subgroup taking beta-blockers versus the subgroup not taking beta-blockers (N = 200), and use of the delta ST/HR index did not improve test performance. For discrimination of severe disease, test accuracy was also unaffected by beta-blockers and was not improved by the delta ST/HR index (N = 454).(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract

To synthesize information on hemodynamic determinants of exercise capacity in patients with chronic heart failure.Relevant studies published from the mid-1960s to the present were identified by a manual search of the English-language literature and by bibliographic review of pertinent articles.Both controlled and observational studies that reported measures of either exercise time or oxygen uptake and hemodynamic variables in patients with heart failure were reviewed for quality and included when relevant to the discussion.Key conclusions or data, or both, were extracted from each article and described.Exercise intolerance is a hallmark of chronic congestive heart failure. Studies have emphasized central factors and indices of systolic ventricular function, but poor relations have been consistently found between these measurements and exercise capacity. Recent data suggest that diastolic function (that is, ventricular filling and compliance) is an important factor affecting the ability to increase cardiac output and determining exercise capacity, but this issue needs further study. A clearer picture of histologic and biochemical abnormalities in skeletal muscle has recently emerged; patients with heart failure show greater glycolysis, reduced oxidative phosphorylation, and reduced oxidative enzyme activity. Vasodilatory abnormalities in heart failure were first described more than 20 years ago, and such abnormalities may underlie recently reported reductions in skeletal muscle blood flow during exercise. Relative hyperventilation is commonly observed during exercise in patients with heart failure and is related to ventilation-perfusion mismatching in the lung due to a higher-than-normal fraction of physiologic dead space. Neurohumoral abnormalities include reductions in beta-receptor density and sensitivity and contribute to reduced inotropic and chronotropic responses to exercise.Systolic function and exercise capacity are unrelated in patients with chronic heart failure, but many hemodynamic abnormalities (including those in the heart, lung, and skeletal muscle) overlap, which leads to exercise intolerance in these patients.

Abstract

Animal studies have consistently shown increased heart strength, size, and vascularity in wild animals compared to domestic animals. While exercise has not been shown to decrease atherosclerosis in either animals or humans, it has been theorized that exercise makes the heart more resistant to ischemia through stimulation of collateral vessel formation and enlargement of already existent coronary arteries. In humans, the benefits and dangers of exercise have been researched with morphological, hemodynamic, and epidemiological studies. Many of these are discussed here as well as the national fitness recommendations made by various health organizations. A summary of the cardiovascular benefits of exercise as supported by the literature is then presented.

Abstract

To evaluate the effects of different methods of detection, exercise modes, protocols, and reviewers on oxygen uptake (VO2) at the ventilatory threshold (ATge), 17 men with heart disease (mean age 59 +/- 6 years) and six healthy men (mean age 60 +/- 11 years) underwent six exercise tests on different days. Each subject performed three treadmill tests (Bruce, Balke, and ramp) and three bicycle ergometer tests (50 W/stage, 25 W/stage, and ramp) in random order. The ventilatory threshold was determined for each of the six exercise tests by three independent, blinded reviewers by means of graphic plots of three commonly used methods of determination: (1) changes in the ventilatory equivalents for VO2 and VCO2, (2) changes in end-tidal oxygen and carbon dioxide pressures, and (3) the intersection of the slope of VCO2 and VO2 (V slope). The largest variability in the ATge was observed with changes in the exercise protocol. The greatest absolute (ml/min) and percentage differences in oxygen uptake at the ATge as a result of changes in protocol, method of determination, and observers were 336 (36%), 125 (12%), and 70 (7%), respectively. The overall intraclass correlation coefficient for VO2 at the ATge among the three reviewers was 0.60 and among the three protocols was 0.85 (p less than 0.01). The V slope method of detection had consistently good agreement among reviewers and was least affected by the protocol. The variance in the ATge (excluding intersubject and error variance) accounted for by differences in protocol, method, and reviewer was 82%, 14%, and 4%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract

To compare the hemodynamic and gas exchange responses of ramp treadmill and cycle ergometer tests with standard exercise protocols used clinically, 10 patients with chronic heart failure, 10 with coronary artery disease who were asymptomatic during exercise, 11 with coronary artery disease who were limited by angina during exercise and 10 age-matched normal subjects performed maximal exercise using six different exercise protocols. Gas exchange data were collected continuously during each of the following protocols, performed on separate days in randomized order: Bruce, Balke and an individualized ramp treadmill; 25 W/stage, 50 W/stage and an individualized ramp cycle ergometer test. Maximal oxygen uptake was 16% greater on the treadmill protocols combined (21.4 +/- 8 ml/kg per min) versus the cycle ergometer protocols combined (18.1 +/- 7 ml/kg per min) (p less than 0.01), although no differences were observed in maximal heart rate (131 +/- 24 versus 126 +/- 24 beats/min for the treadmill and cycle ergometer protocols, respectively). No major differences were observed in maximal heart rate or maximal oxygen uptake among the various treadmill protocols or among the various cycle ergometer protocols. The ratio of oxygen uptake to work rate, expressed as a slope, was highest for the ramp tests (slope +/- SEE ml/kg per min = 0.80 +/- 2.5 and 0.78 +/- 1.7 for ramp treadmill and ramp cycle ergometer, respectively). The slopes were poorest for the tests with the largest increments in work (0.62 +/- 4.0 and 0.59 +/- 2.8 for the Bruce treadmill and 50 W/stage cycle ergometer, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract

To compare angina and ST-segment depression during exercise testing, as markers for coronary artery disease.Retrospective analysis of exercise test responses and cardiac catheterization results.A U.S. Veterans Affairs medical center.Four hundred and sixteen men who were referred for the evaluation of symptoms, postmyocardial infarction testing, or both. Two hundred patients had no clinical or electrocardiographic evidence of previous myocardial infarction, whereas 216 were survivors of a previous myocardial infarction.All patients did a standard exercise test and had diagnostic coronary angiography with ventriculography within an average of 32 days (range, 0 to 90 days) of their exercise test.Two hundred patients without a previous myocardial infarction were divided into four groups: the no ischemia group had 80 patients; the angina pectoris only group had 23 patients; the silent ischemia group had 40 patients; and the ST-segment depression and angina pectoris group had 57 patients. In patients without a previous myocardial infarction, exercise-induced ST-segment depression was a better marker than exercise-induced angina for the presence of any coronary artery disease (P less than 0.005). Patients with symptomatic exercise-induced ischemia had a higher prevalence of severe coronary artery disease than did those with only silent ischemia (30% compared with 20%; 95% CI, - 7.3% to 27.0%; P = 0.005). For the 216 survivors of a myocardial infarction, divided into the same four groups, ST-segment depression again was a better marker for the presence of severe coronary artery disease compared with angina alone (P = 0.08). The prevalence rates of severe coronary artery disease in the no ischemia plus myocardial infarction group, the angina pectoris only plus myocardial infarction group, the silent ischemia plus myocardial infarction group, and the ST-segment depression and angina pectoris plus myocardial infarction group were 10%, 9%, 23%, and 32%, respectively (P less than 0.01).Exercise-induced ST-segment depression is a better marker for coronary artery disease than is exercise-induced angina. Symptomatic ischemia during the exercise test is a better marker for severe coronary artery disease than is silent ischemia.

Abstract

Exercise-induced ventricular tachycardia during exercise testing is considered to increase risk during testing. Moreover, exercise-induced ventricular tachycardia has been considered to confer a poor prognosis although this has not been specifically studied. On a retrospective review of 3351 patients who had undergone routine clinical exercise testing between September 1984 and June 1989, we identified 55 patients with exercise-induced ventricular tachycardia. The mean follow-up was 26 months (range, 2 to 58 months). Fifty patients had nonsustained ventricular tachycardia during exercise testing and one of these patients died due to congestive heart failure during the follow-up period. Five patients had sustained ventricular tachycardia during exercise testing and one died suddenly 7 months after the test. Ventricular tachycardia was reproduced in only two of the 29 patients who underwent repeated exercise testing. Ventricular tachycardia during routine clinical exercise testing occurred rarely (prevalence of 1.5%) and was not associated with complications during testing. The total mortality in the exercise-induced ventricular tachycardia group (3.6%) was not significantly different from the mortality in the entire population (5.1%). Nonsustained ventricular tachycardia occurring during clinical exercise testing is not an independent marker of a poor prognosis.

Abstract

Exercise trials in cardiology are often hindered by inconsistent approaches to exercise testing. These inconsistencies include the choice of exercise protocol, exercise end points, points of analysis, and absence or misuse of gas exchange data. Gas exchange techniques greatly enhance the accuracy with which cardiopulmonary function is assessed by exercise. Commonly used protocols are not always appropriate for all patients or all studies. Both cardiovascular disease and the exercise protocol can have an important impact on the relation between changes in work rate and oxygen uptake. Ramp protocols appear to offer the greatest promise for assessing cardiopulmonary function. Analyzing hemodynamic and gas exchange responses at several points submaximally, in addition to those at peak exercise, can add important information concerning the efficacy of a drug. A great deal of confusion continues to hinder the application of the gas exchange anaerobic threshold, and many of the commonly used testing end points are not reliable.

Abstract

To evaluate variability in the reported accuracy of fluoroscopically detected coronary calcific deposits for predicting angiographic coronary disease, we applied meta analysis to 13 consecutively published reports comparing the results of cardiac fluoroscopy with coronary angiography. Population characteristics and technical and methodologic factors were analyzed. Sensitivity and specificity for predicting serious coronary disease compare quite well with those from the literature on the exercise ECG and the exercise thallium scintigram. Sensitivity increases and specificity decreases more significantly with patient age, and sensitivity is paradoxically lower in laboratories testing patients with more severe disease, as well as when 70% rather than 50% diameter narrowing is used to define angiographic disease. Work-up and test review bias were also significantly related to reported accuracy.

Abstract

Exogenous fructose 1,6-diphosphate (FDP), a glycolytic intermediate, increases blood ATP and 2,3 diphosphoglycerate levels, facilitates the dissociation of oxygen from hemoglobin, and increases red blood cell flexibility. These mechanisms explain why it has been effective in enhancing energy production in a variety of ischemic conditions. The present study was undertaken to determine whether FDP could enhance oxygen supply and thus improve exercise performance in patients with peripheral vascular disease. Ten male patients (mean age 63 +/- 5 years) with peripheral vascular disease performed symptom-limited exercise testing after randomized, double blind infusion of either 200 mg/kg body weight FDP or placebo. Data were evaluated at rest, at a matched submaximal workload (2-3 MPH/0% grade), and at peak exercise, defined as the occurrence of moderately severe claudication. No differences were observed in heart rate, blood pressure, gas exchange data, time to the onset of claudication or peak exercise, or lactate and 2,3 diphosphoglycerate levels. In contrast to previous studies performed among patients with peripheral vascular disease and other studies using more severe hypoxic conditions, FDP did not affect the respiratory gas exchange or exercise capacity of patients with exertional claudication.

Abstract

The objective of our study was to compare the discriminating power of a proposed ST segment/heart rate index with that of a standard method of assessing exercise-induced ST segment depression for diagnosing coronary artery disease. We used a cross-sectional retrospective analysis of exercise test and coronary angiographic data. The study took place in a 1,200-bed Veterans Affairs Medical Center; participants were 328 male patients who had undergone both a sign and symptom-limited treadmill test and coronary angiography. The sensitivity of the ST segment/heart rate index was 54% at a cut point of 0.021 mm/(beats/min), corresponding to a specificity of 73%. The standard visual ST segment analysis had a sensitivity of 58% at this same specificity, which corresponded to an ST segment cut point of 1-mm depression relative to rest (p = NS). Similarly, for diagnosing three-vessel or left main coronary disease, no significant difference was found between the sensitivities or the two measurements at cut points of equivalent specificity. In this consecutive series of patients presenting for routine clinical testing, the ST segment/heart rate index did not improve the diagnostic accuracy of the exercise test for identifying the presence or severity of coronary artery disease relative to standard visual criteria.

Abstract

To investigate the effects of complete and incomplete revascularization on the response to exercise, 25 patients underwent symptom-limited exercise testing with continuous assessment of gas exchange a mean of 5 +/- 4 days prior to and 18 +/- 12 days following percutaneous transluminal coronary angioplasty. All antianginal medications were discontinued for testing. Revascularization was considered complete if all stenoses were reduced to less than 50% diameter (13 patients), and incomplete if one or more stenoses remained (12 patients). Consistent improvements in ST-segment depression were observed after angioplasty at matched submaximal exercise levels (mean range 0.5-0.8 mm; p less than 0.05), and were accompanied by a reduction in angina. Significant increases in heart rate and systolic blood pressure were observed at peak exercise following angioplasty in both groups. Gas exchange variables were significantly improved at maximal exercise, with a similar increase in oxygen uptake observed in both groups following angioplasty (mean increase 3.3-3.7 ml/kg/min; p less than 0.01). Thus, incomplete revascularization following coronary angioplasty resulted in hemodynamic, electrocardiographic, symptomatic, and gas exchange responses to exercise that were comparable to complete revascularization.

Abstract

To clarify the predictive value of exercise-induced ST-segment depression occurring in recovery only, and to determine whether the addition of recovery data improves the interpretation of the exercise test.Retrospective analysis of data collected during exercise testing and coronary angiography.A 1000-bed Veterans Affairs Medical Center.The study included 328 male patients who had had both a sign- or symptom-limited treadmill test and coronary angiography.Of the 168 patients who had abnormal ST-segment responses, 26 had such responses only during recovery. The positive predictive value of this pattern for significant angiographic disease (84%) was not statistically different from the predictive value of ST depression occurring during exercise (87%). Inclusion of ST depression during recovery significantly increased the sensitivity of the exercise test from 50% to 59% (P = 0.01) without a change in predictive value. In addition, ST-segment depression occurring only during exercise is usually associated with less-severe angiographic coronary artery disease.The occurrence of ST-segment depression during the recovery period only, does not generally represent a "false-positive" response. The inclusion of findings from this period increases the diagnostic yield of the exercise test. Previously proposed exercise test scores, as well as exercise electrocardiography (ECG) analysis done in conjunction with scintigraphy, have a falsely lowered sensitivity that could be increased by considering ST-segment changes occurring in recovery.

Abstract

The failure of oxygen uptake to increase with increasing work has been considered a marker of the limits of the cardiopulmonary system for many years. However, the concept has suffered from inconsistencies in definition, criteria, and data sampling, all of which affect the interpretation of the relation between changes in work and oxygen uptake. To evaluate the response and reproducibility of the slope in oxygen uptake at peak exercise, six subjects (mean age, 33 +/- 6 years) performed two individualized ramp treadmill tests on separate days. During exercise, oxygen uptake (for a given sample of 30 eight-breath running averages) was regressed with time and the slope was calculated. Maximal oxygen uptake, maximal heart rate and maximal perceived exertion were reproducible from day 1 to day 2 (mean difference, 0.4 ml/kg/min, 1.0 beats per minute, and 0.2 for maximal oxygen uptake, heart rate, and maximal perceived exertion, respectively [not significant]). Considerable variability in the slopes was observed during each test and from day to day. This occurred despite the use of large gas exchange samples, averaging techniques, and constant, consistent changes in external work. A plateau, defined as the slope of an oxygen uptake sample at peak exercise that did not differ significantly from a slope of zero, was not a consistent finding within subjects between days. We conclude that marked variability in the slope of the change in oxygen uptake occurs throughout progressive exercise, despite the use of large samples and a linear change in external work. These findings appear to preclude the determination of a plateau by common definitions.

Abstract

To evaluate the variability in the reported accuracy of the exercise electrocardiogram (ECG) for predicting severe coronary disease, meta analysis was applied to 60 consecutively published reports comparing exercise-induced ST depression with coronary angiographic findings. The 60 reports included 62 distinct study groups comprising 12,030 patients who underwent both tests. Both technical and methodologic factors were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity 81% [range 40% to 100%, SD 12%]; mean specificity 66% [range 17% to 100%, SD 16%]). All three variables found to be significantly and independently related to sensitivity were methodologic (the exclusion of patients with right bundle branch block, the comparison with another exercise test thought to be superior in accuracy and the exclusion of patients taking digitalis). Exclusion of patients with right bundle branch block and comparison with a "better" exercise test were both significantly associated with sensitivity for the prediction of triple vessel or left main coronary artery disease. Adjustment of exercise-induced ECG changes for changes in heart rate was strongly associated with the specificity for critical disease (partial R2 = 0.436, p = 0.0001).

Abstract

The purposes of this study were 1) to determine the prognosis of silent ischemia in an unselected group of patients referred for exercise testing, and 2) to assess whether age or the presence of myocardial infarction or diabetes mellitus influences the prevalence of silent myocardial ischemia during exercise testing. The design was retrospective, with a 2 year mean follow-up period. The study group consisted of 1,747 predominantly male in-patients and outpatients referred for exercise testing at a 1,200 bed Veterans Administration hospital. The main result was that the mortality rate was significantly greater (p = 0.02) among patients with abnormal ST segment depression than in patients without ST depression. The presence or absence of angina pectoris during exercise testing was not significantly related to death. The prevalence of silent ischemia was not significantly different among patients categorized according to myocardial infarction or diabetes mellitus status, but was directly related to age. It is concluded that, in patients with an ischemic ST response to exercise testing, the presence or absence of angina pectoris during the test does not alter the risk of death. The prevalence of silent ischemia during exercise testing is not statistically different among patients with recent, past or no myocardial infarction or with insulin-dependent or noninsulin-dependent diabetes mellitus.

Abstract

Exercise tolerance in patients with normal cardiac function can improve with an exercise program. Controversy exists whether this is also true for patients with congestive heart failure (CHF). The limiting symptoms in patients with CHF are shortness of breath and fatigue. Hemodynamic parameters do not correlate well with exercise capacity in patients with CHF. These symptoms may be more related to factors that cause fatigue during exercise than to hemodynamic parameters or even to changes in pulmonary capillary pressure. The factors that cause symptoms include an increased lactate production and metabolic and blood flow abnormalities in the skeletal muscle. Exercise training can improve vasodilation and oxidation capacity, thereby reducing lactate production. Exercise programs may improve exercise capacity in the majority of patients with CHF due to coronary artery disease or idiopathic cardiomyopathy. However, certain patients with ischemia and with anterior infarctions may experience a detrimental effect on their cardiac function. Further studies are needed to better enable recognition of these patients but until this is possible, good clinical judgement must suffice.

DOES THE REST ELECTROCARDIOGRAM AFTER MYOCARDIAL-INFARCTION DETERMINE THE PREDICTIVE VALUE OF EXERCISE-INDUCED ST DEPRESSION - A 2-YEAR FOLLOW-UP-STUDY IN A VETERAN POPULATIONJOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGYKlein, J., Froelicher, V. F., Detrano, R., Dubach, P., Yen, R.1989; 14 (2): 305-311

Abstract

The failure of exercise-induced ST segment depression to consistently predict prognosis in patients after myocardial infarction could be a result of population differences and the rest electrocardiogram (ECG). These hypotheses were tested by studying 198 veterans who survived a myocardial infarction, underwent a submaximal predischarge treadmill exercise test and were followed up for cardiac events for 2 years. During the 2 years, 29 deaths, 19 reinfarctions and 28 revascularization procedures were documented. The prevalence of death or reinfarction was two times higher in patients who had exercise-induced ST depression than in patients who did not. However, in the 55 patients without Q waves, the risk increased to 11 times for an abnormal ST response. These findings suggest that exercise-induced ST depression only predicts high risk in patients after myocardial infarction whose ECG at rest does not exhibit Q waves and that differences in the prevalence of rest ECG patterns are the most likely explanation for the failure of agreement among prior studies.

Abstract

A new discriminant function model for estimating probabilities of angiographic coronary disease was tested for reliability and clinical utility in 3 patient test groups. This model, derived from the clinical and noninvasive test results of 303 patients undergoing angiography at the Cleveland Clinic in Cleveland, Ohio, was applied to a group of 425 patients undergoing angiography at the Hungarian Institute of Cardiology in Budapest, Hungary (disease prevalence 38%); 200 patients undergoing angiography at the Veterans Administration Medical Center in Long Beach, California (disease prevalence 75%); and 143 such patients from the University Hospitals in Zurich and Basel, Switzerland (disease prevalence 84%). The probabilities that resulted from the application of the Cleveland algorithm were compared with those derived by applying a Bayesian algorithm derived from published medical studies called CADENZA to the same 3 patient test groups. Both algorithms overpredicted the probability of disease at the Hungarian and American centers. Overprediction was more pronounced with the use of CADENZA (average overestimation 16 vs 10% and 11 vs 5%, p less than 0.001). In the Swiss group, the discriminant function underestimated (by 7%) and CADENZA slightly overestimated (by 2%) disease probability. Clinical utility, assessed as the percentage of patients correctly classified, was modestly superior for the new discriminant function as compared with CADENZA in the Hungarian group and similar in the American and Swiss groups. It was concluded that coronary disease probabilities derived from discriminant functions are reliable and clinically useful when applied to patients with chest pain syndromes and intermediate disease prevalence.

Abstract

To assess the accuracy of the Bayesian computer program CADENZA for the prediction of coronary artery disease, the authors examined the probabilities generated by the application of this program to the clinical and noninvasive test results of 303 patients in a private referral center and 199 patients in a veterans' hospital. These probabilities were compared with those produced by applying a six-variable discriminant function derived by logistic regression at the private referral center. Two statistical approaches were employed in evaluating the relative performances of the Bayesian program and the discriminant function. The first of these involved the sorting of patients in both test groups into ascending deciles of probability and comparing expected probability with observed angiographic disease prevalence in each decile. The second involved the calculation and comparison of a standardized reliability measure. The latter was significantly lower for the discriminant function both at the private hospital (0.200 for the discriminant function versus -17.5 +/- 1.96 for the Bayesian program) and at the veterans' hospital (-0.8 +/- 1.96 for the discriminant function versus -11.3 for Bayesian program). This suggests that the discriminant function is significantly superior to the Bayesian algorithm CADENZA for predicting coronary artery disease probabilities in subjects who have relatively high pretest disease probabilities.

Abstract

To evaluate the variability in the reported diagnostic accuracy of the exercise electrocardiogram, we applied meta-analysis to 147 consecutively published reports comparing exercise-induced ST depression with coronary angiography. These reports involved 24,074 patients who underwent both tests. Population characteristics and technical and methodologic factors, including publication year, number of electrocardiographic leads, exercise protocol, use of hyperventilation, definition of an abnormal ST response, exclusion of certain subgroups, and blinding of test interpretation were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity, 68%; range, 23-100%; SD, 16%; and mean specificity, 77%; range, 17-100%; SD, 17%). The four study characteristics found to be significantly and independently related to sensitivity were the treatment of equivocal test results, comparison with a "better" test such as thallium scintigraphy, exclusion of patients on digitalis, and publication year. The four variables found to be significantly and independently related to specificity were the treatment of upsloping ST depressions, the exclusion of subjects with prior infarction or left bundle branch block, and the use of preexercise hyperventilation. Stepwise linear regression explained less than 35% of the variance in sensitivities and specificities reported in the 147 publications. There is wide variability in the reported accuracy of the exercise electrocardiogram. This variability is not explained by information reported in the medical literature.

Abstract

Serial submaximal treadmill tests are often used to evaluate the efficacy of therapy in patients with atrial fibrillation. Since the response to serial tests can be influenced by a 'learning phenomenon', we performed maximal exercise tests on 9 patients (mean age 63 +/- 4 years) with chronic atrial fibrillation. Points of analysis for the initial and follow-up treadmill exercise tests were 3 mph/0% grade, the gas exchange anaerobic threshold, and maximal exertion. Significant (p less than 0.05) reductions in ventilation (l/min) and oxygen uptake (ml/kg/min) were observed on follow-up at a standard submaximal work load of 3.0 mph/0% grade and at the gas exchange anaerobic threshold. There was no significant alteration in these variables at maximal exertion. A reduction in heart rate was observed throughout exercise during the follow-up test with the most marked reduction (21 beats/min) occurring at 3.0 mph/0% grade. There were no differences in respiratory exchange ratio or systolic blood pressure at any point. The reduction in submaximal heart rate and gas exchange variables without a significant change in these variables at maximal exertion is consistent with a learning effect. Therefore, studies comparing consecutive submaximal exercise test responses in patients with atrial fibrillation can be misleading.

Abstract

Failure to objectively assess the effect of digitalis on exercise capacity has resulted in controversy regarding its use in patients with chronic congestive heart failure. To clarify this situation, maximal treadmill testing with respiratory gas exchange analysis was performed on 11 patients (mean age 57 +/- 9 years) with chronic congestive heart failure with and without digoxin therapy. Ten of the 11 had a consistent third sound gallop, and the mean ejection fraction of the group was 24 +/- 10%. Rest heart rate was significantly higher (91 +/- 16 versus 102 +/- 16 beats/min; p less than 0.05) and rest systolic blood pressure was significantly reduced in the absence of digoxin (130 +/- 23 versus 121 +/- 15 mm Hg; p less than 0.05). No differences in heart rate or blood pressure were observed during exercise. Significant increases in ventilatory oxygen uptake were observed with digoxin submaximally (3.0 mph, 0% grade), at the gas exchange anaerobic threshold and at maximal exercise (mean increase of 2.6 ml/kg per min; p less than 0.02). An improvement in the estimated ratio of ventilatory dead space to tidal volume (VD/VT), an index of physiologic efficiency, occurred throughout exercise during digoxin therapy, and there was a significant negative correlation between the change in maximal oxygen uptake and change in maximal estimated VD/VT (r = -0.63; p less than 0.05). Thus, digoxin therapy is associated with a significant improvement in exercise capacity in patients with chronic heart failure, most likely due to an improved matching of ventilation to perfusion.

Abstract

The objective of this study was to predict the prognosis of patients who become symptomatic after having undergone coronary artery bypass grafting (CABG) using clinical and exercise test responses. A retrospective analysis was performed of all veterans referred for clinical indications to a Veterans Administration Medical Center for a treadmill test after having undergone CABG. Of 2,044 patients who were exercise tested from April 1984 to May 1987, 296 had previously undergone CABG. Clinical data considered included age, sex, medication and symptom status, history of myocardial infarction, type of myocardial infarction and time from CABG. The exercise test responses considered were MET level, maximal heart rate, maximal systolic blood pressure, chest pain pattern and ST-segment response. During a 2-year follow-up after exercise testing, there were 15 deaths, 11 nonfatal myocardial infarctions, 6 repeat CABGs and 3 percutaneous transluminal coronary angioplasties. Although MET level and maximal heart rate were significantly related to prognosis and no patient who exceeded 8 METs died, the predictive power of these exercise test responses was low and ST-segment depression was not predictive at all. The inability of the exercise electrocardiogram to predict cardiac events in patients after CABG requires the use of other methods of testing to identify those who need invasive studies and intervention.

Abstract

To investigate the ideal sampling interval for the estimation of heart rate (HR) at rest and during exercise in atrial fibrillation (AF), maximal exercise testing with continuous electrocardiographic acquisition was performed in 10 patients with chronic AF (mean age 66 +/- 4 years) and 10 subjects in normal sinus rhythm (mean age 31 +/- 6 years). Measurements of HR were obtained at 9 different sampling intervals (1, 2, 3, 6, 10, 15, 20, 30 and 60 seconds) at rest and 7 different sampling intervals (1, 2, 3, 6, 10, 15 and 20 seconds) during the last 30 seconds of each minute during exercise. The HR obtained from each interval was compared with true HR (determined by a 4-minute sample at rest and by the last 30 seconds of each minute during exercise). Among patients with AF, large differences were observed between the HR obtained and true HR, both at rest and during exercise, using small sampling intervals. The mean of these differences ranged between 16 +/- 11 beats/min (range 14 to 22) using 1-second sampling intervals and 2.2 +/- 2.0 beats/min (range 1.6 to 4.4) using 20-second sampling intervals during progressive exercise. Variability of the HR obtained from a given random sample was also high when short sampling intervals were used among patients with AF. These observations were contrasted by subjects in normal sinus rhythm, among whom neither variability nor measurement error were influenced remarkably by changing the sampling interval or increasing HR.

Abstract

The objective of this study was to demonstrate the causes, optimal definition, and predictive value of exercise-induced hypotension occurring during treadmill testing. This study included all patients referred for clinical reasons to the Long Beach Veterans Administration Medical Center treadmill laboratory and then followed for a 2-year period for cardiac events. The population consisted of 2,036 patients who underwent testing from April 4, 1984, to May 7, 1987, 131 of whom exhibited exercise-induced hypotension (6.4%). We found that exercise-induced hypotension is usually related to myocardial ischemia or myocardial infarction, is best defined as a drop in systolic blood pressure during exercise below the standing preexercise value, and indicates a significantly increased risk for cardiac events (3.2-fold, p less than 0.005). This increased risk was not found in those having no previous myocardial infarction or no signs or symptoms of ischemia during the exercise test, and the increased risk was also not found in those undergoing a treadmill test within 3 weeks after a myocardial infarction. Exercise-induced hypotension appeared to be reversed by revascularization procedures, but confirmation of a beneficial effect on survival requires a randomized trial. The clinical importance of this study is that we have demonstrated that a drop in systolic blood pressure below standing preexercise values during treadmill testing indicates an increased risk for cardiac events except in certain subsets of patients.

Abstract

Accurate use and interpretation of exercise test results depend on an understanding of physiologic principles, meticulous attention to proper methodology, and realization of the appropriate applications and limitations of testing. Understanding the relationship between myocardial and ventilatory oxygen consumption and exercise test variables will aid in the diagnosis and prognostic evaluation. Use of proper methodology in preparing the patient, performing the examination, and interpreting the results is critical to obtaining the maximum information with maximum safety for each individual patient. Improvements in methodology including the use of the Borg scale to estimate individual effort, abandonment of the predicted maximum heart rate, and the increased use of ventilatory oxygen uptake measurements should be applied. Exercise capacity should not be reported in total time but rather as the VO2 or MET equivalent of the workload achieved. This permits the comparison of the results of many different exercise testing protocols. The most useful exercise ECG variable for the diagnosis of coronary artery disease remains the ST segment shift. Unfortunately, it is not as helpful in localizing myocardial ischemia. Diagnostic accuracy can be improved by adjusting ST depressions for exercise-induced heart rate increase. Accuracy can be further increased by combining ECG, clinical, and radionuclide variables in probabilistic formulas that retain the independent diagnostic information from each variable and accurately predict disease probability. To avoid errors in clinical decision making, care must be used to insure that the mathematical formula used was derived from a population of patients that is similar to those being tested. The clinical applications for exercise testing include diagnosis of patients with chest pain syndromes, determination of disease severity, and prognosis in patients with known coronary artery disease, evaluation of arrhythmias, screening of asymptomatic patients, and evaluation of medical, surgical, and angioplastic therapy for coronary disease. In spite of studies involving thousands of patients, controversy exists regarding the diagnostic power of exercise testing. The large differences in reported accuracies are largely due to methodologic problems that have been encountered by various investigators. Clinicians should be made aware of these problems when reading the literature on ECG and radionuclide exercise testing. Such awareness will help them understand the limitations of these noninvasive procedures.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract

Numerous investigators have demonstrated that responses to exercise testing enable prediction of the severity of underlying coronary disease and the patient's prognosis. However, exercise testing cannot predict angiographic findings or a poor prognosis with absolute certainty. Because survival can only be improved in specific clinical subsets of patients, it is important to carefully select for catheterization those in whom intervention can improve both quality and quantity of life. To deliver cost-effective health care, an effort has been made to use decision analysis to select those who should undergo cardiac catheterization. Decision analysis depends on reliable information regarding the predictive accuracy of the exercise test. Thus, this review is timely. Recent studies investigating the prognostic value of the exercise test are reviewed in this monograph. Patients include those recovering from a recent myocardial infarction (MI), those with stable coronary heart disease (including studies that have considered coronary angiographic findings, cardiac end points, and/or improved survival with coronary artery bypass surgery), and apparently healthy individuals. From this review, we conclude that silent ischemia induced by exercise testing in apparently healthy men is not as predictive of a poor outcome as once thought. Also, the use of the exercise test for screening is even more misleading than previously appreciated because of the higher rate of false positive results. Review of the 24 available studies of exercise testing in post-MI patients demonstrates that clinical judgment can be used to identify the high-risk patients, and that ST-segment shifts are not as predictive of high risk as an abnormal systolic blood pressure response or a poor exercise capacity. In patients with stable coronary heart disease, studies considering angiographic findings, cardiac events, and the differential outcome of coronary artery bypass surgery as compared with medical therapy have shown the exercise test to have prognostic power. From this perspective, it is obvious that there is much information supporting the use of exercise testing as the first noninvasive step after the history, physical examination, and resting electrocardiogram in the prognostic evaluation of patients with coronary artery disease. It accomplishes both purposes of prognostic testing: to provide information regarding the patient's status, and to help make recommendations for optimal management. The exercise test results help us make reasonable decisions for selection of patients who should undergo coronary angiography-including quality-of-life issues.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract

Before there is widespread clinical application of the high-frequency ECG, differences resulting from the leads used and the measurement criteria for late potentials must be resolved. Therefore 113 consecutive patients without resting QRS conduction abnormalities referred for Holter monitoring were studied. Four different lead systems were used: a standard bipolar orthogonal lead system and three bipolar lead systems mapping the left ventricle. Measurements made of late potentials included normal and high-frequency QRS duration, their difference, the duration of low-amplitude signals (less than 40 uV) in the terminal QRS, and the root mean square of the last 40 msec of the high-frequency QRS duration. We found that the left ventricular leads tended to give more abnormal measurements than the orthogonal system and that the various measurements failed to agree with each other. In addition, even in this population in which abnormalities of QRS conduction were excluded, the late potential measurements tended to be more abnormal as QRS duration lengthened. These differences in lead systems and measurement criteria must be considered when clinically applying information regarding late potentials measured from the high-frequency ECG.

Abstract

The accuracy and applicability of probability analysis to the diagnosis of coronary artery disease is still an open question. Although earlier criticisms are well taken, much of the resistance to the application of probability analysis is based on tradition, rather than logic. Probabilistic algorithms, like any new technology, must be researched and developed and then withstand the test of time. They should not be dismissed simply because they are not traditional. On the other hand, probability analysis in the diagnosis of coronary artery disease must not be accepted just because it is attractive or because it appears to simplify clinical decisions. Application of probabilistic approaches should depend on their accuracy. There is evidence that results of tests and clinical data are not statistically independent. There is also evidence that sensitivities and specificities derived from pooled literature cannot be appropriately applied to just any patient in a particular institution. This is due to variability in the population of patients, a lack of standardization of testing methods, and methodologic problems in reporting results of sensitivities and specificities. In a large institution, where probabilistic formulae can be derived with some degree of confidence, probability analysis has an application today. Discriminant functions will be more accurate than Bayesian formulas, but whatever method one chooses, one must be certain that the parameters used are appropriate. Where the institution is not large enough to generate such a data base, there is presently no accurate approach to the estimation of the probability of coronary disease.

Abstract

To evaluate the comparative effects of methodologic factors on the reported accuracies of two standard exercise tests, 56 publications comparing the exercise thallium scintigram with the coronary angiogram were analyzed for conformation to five methodologic standards. Analyzed were adequate definition of study group, avoidance of a limited challenge group, avoidance of workup bias, and blinded analysis of the coronary angiogram and myocardial scintigram. Study group characteristics and technical factors were also reviewed. Better conformation with methodologic standards was found than has been reported previously for treadmill exercise testing. Furthermore, study group characteristics and technical factors were better predictors of sensitivity and specificity than were methodologic deficiencies. Only workup bias and test blinding were significantly associated with test accuracy. The percentage of patients with previous myocardial infarction had the highest correlation and was independently and directly related to sensitivity and inversely related to specificity.

Abstract

Technical and methodological factors might affect the reported accuracies of diagnostic tests. To assess their influence on the accuracy of exercise thallium scintigraphy, the medical literature (1977 to 1986) was non-selectively searched and meta-analysis was applied to the 56 publications thus retrieved. These were analyzed for year of publication, sex and mean age of patients, percentage of patients with angina pectoris, percentage of patients with prior myocardial infarction, percentage of patients taking beta-blocking medications, and for angiographic referral (workup) bias, blinding of tests, and technical factors. The percentage of patients with myocardial infarction had the highest correlation with sensitivity (0.45, p = 0.0007). Only the inclusion of subjects with prior infarction and the percentage of men in the study group were independently and significantly (p less than 0.05) related to test sensitivity. Both the presence of workup bias and publication year adversely affected specificity (p less than 0.05). Of these two factors, publication year had the strongest association by stepwise linear regression. This analysis suggests that the reported sensitivity of thallium scintigraphy is higher and the specificity lower than that expected in clinical practice because of the presence of workup bias and the inappropriate inclusion of post-infarct patients.

Abstract

An exercise ECG analysis program was developed over 15 years on a number of mainframes, minicomputers and, most recently, microcomputer-based systems. It has been rehosted into both Motorola MC68000 and Intel 80286 microprocessor-based development systems and is currently used with a removable 200 Mbyte optical disk (Write-Once-Read-Many, WORM) based data-logger system that can record and store all 12 leads simultaneously and continuously for an entire exercise test (up to 38 minutes). Data is acquired with 12-bit A/D resolution at 500 samples/sec. All ECG data and patient information are archived on the optical disk for later off-line recall and analysis on a PC or real-time replay through a D/A converter. Recorded ECG signals are at patient levels so they can be replayed through the patient cable box on any commercial system. Current development includes both simultaneous on-line processing and storage of 12-lead ECG data and off-line processing and development performed on the long-term, continuous ECG data being archived on optical disk. Patient medical histories and clinical information are separately entered into an applications database, where ECG measures and test results are later included. This new optical disk based exercise ECG database contains more than 600 complete exercise tests and is projected to increase to nearly 3,000 within 2 years.

Abstract

To assess the accuracy of Bayesian probability analysis for the prediction of coronary artery disease, post-test probabilities were generated by the application of three Bayesian algorithms to the clinical and noninvasive test results of 199 patients undergoing angiography in a veterans' hospital. All assumed conditional independence but each used different pre-test and conditional probabilities. Two statistical approaches were employed: (1) Sorting of patients in ascending deciles of probability and comparing expected and observed probabilities in each decile. (2) Calculation of normally distributed reliability statistics which do not depend on probability subsets and the comparison of resulting probability distributions using these statistics. Both statistical approaches revealed that the Bayesian algorithms overestimated disease probability when it was high and underestimated it when low. Though all three algorithms were frequently incorrect, they differed significantly in their accuracies, suggesting that errors in Bayesian analysis are caused by factors other than the assumption of independence. The errors may be due to differences in sensitivity and specificity of tests applied in different institutions.

Abstract

One common variety of exercise-induced artifact is baseline wander resulting from movement, respiration, and poor electrode contact. Although filters can be designed to remove much of this baseline variation, they will distort the low-frequency components of the ECG complex, such as the TP-segment, the PR-segment, and, most problematically, the ST-segment. The ST-segment is the most diagnostically relevant measure of the ECG taken during exercise. While linear baseline interpolation and removal may be adequate at lower heart rates, they also will introduce significant distortions. This is particularly evident when excessive nonlinear wander is present, as seen at higher heart rates and respiration rates. A nonlinear, third-order, polynomial estimator of baseline wander, known as the cubic spline, has been used for nearly 15 years. It is a very robust technique applied to exercise ECG recordings. Since the cubic spline is not a filter and use an a priori knowledge of the shape of the ECG signal, it estimates the true baseline and avoids distortion better. The more common implementations of this technique use relatively short ECG recordings. With the advent of increasing power in computerized ECG systems, the implementation of the cubic spline algorithm for removing baseline wander in continuous, longer-duration ECG records and in real-time processing is being attempted. However, the correct application of the cubic spline to continuous recordings is not straightforward and involves a number of previously unforeseen difficulties. The accuracy and resolution of both floating point and integer operations is critical during long-term application of the cubic spline function.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract

Decision analysis is being applied to medical practice in order to achieve cost efficacy in health care delivery. Critical to this process is establishing the diagnostic and prognostic accuracy of medical tests and the effectiveness of interventions. Meta-analysis is an approach that applies statistical methods to groups of studies in order to extract consensus results. Electronic spreadsheets facilitate meta-analysis with their ability to store, sort, graph, and mathematically manipulate both the methodologic approaches and clinical findings of seemingly disparate studies. As an example, this application is demonstrated with an analysis of studies that were performed to evaluate the prognostic value of exercise testing in patients recovering from a myocardial infarction. The following conclusions were reached: (1) patients excluded from exercise testing have the highest mortality; (2) only subsets of patients have been tested resulting in highly selected patient samples that make findings difficult to generalize; (3) of the five exercise test responses, only an abnormal systolic blood pressure response and a poor exercise capacity predicted risk more frequently than by chance; (4) submaximal or predischarge testing has greater predictive power than postdischarge or maximal testing; and (5) exercise-induced ST segment depression only appears to be predictive of increased risk in patients with inferior-posterior myocardial infarctions. This approach to combining studies is important since even careful analysis of a single study cannot elucidate all of the complex interactions and selective biases that have occurred. However, comparison of many heterogeneous studies is at best an arduous and time-consuming task. This approach to using electronic spreadsheets to collate and analyze multiple studies facilitates recognition of the population characteristics, clinical factors, and methodologic considerations that affect outcome and allows the quick inclusion of additional studies for re-analysis and interpretation.

DETECTION AND MEASUREMENT OF THE P-WAVE AND T-WAVE DURING EXERCISE TESTING USING COMBINED HEURISTIC AND STATISTICAL-METHODSJOURNAL OF ELECTROCARDIOLOGYFRONING, J. N., Froelicher, V. F.1987; 20: 145-156

Abstract

Accurate detection and measurement of the P-wave and T-wave components of the ECG complex have been difficult and often avoided in computerized ECG analysis. This is particularly so during exercise testing where T-P fusion occurs during higher heart-rates. By combining advanced pattern-recognition techniques, statistical measurements and empirically based heuristic decision-making logic, our ECG Analysis program has been able to reliably detect, measure and track these components during exercise testing to a degree surpassing visual detection by highly experienced readers. Complete analysis of each consecutive record gathered during the exercise test is performed and a data-base of measurements and parameters is created for reference comparison of previous results at each analysis step to current measurements. Thus, evaluation of each current record for appropriate and accurate analysis is based on an expert system approach which is constantly updated and can adjust itself to individual ECG morphology as the test progresses. Preliminary attempts are also being made to separate, extract and normalize the P-wave and T-wave during fusion for better understanding and comparison of changes which occur at high heart-rates. Theoretical and clinical reasons related to the detection and measurements of the P-wave and T-wave during exercise testing are also discussed.

Abstract

Beta-adrenergic blocking agents are commonly used in combination with digitalis to control excessive heart rate during exercise in patients with chronic atrial fibrillation. However, little is known about the effect of beta-adrenergic blockade on exercise capacity in these patients. Accordingly, a randomized, double-blind, cross-over placebo-controlled study was performed to assess the efficacy of celiprolol, a new cardioselective beta-blocker with partial intrinsic sympathomimetic activity, on exercise performance in nine men with chronic atrial fibrillation. All but one patient was receiving maintenance digitalis during the study. Heart rate, blood pressure and gas exchange variables were measured at rest and during treadmill exercise testing while the patients were receiving maintenance celiprolol or placebo. Significant reductions in heart rate and systolic blood pressure compared with control values were observed at submaximal exercise, at the gas exchange anaerobic threshold and at maximal exertion while the patients were taking celiprolol. However, oxygen uptake at the gas exchange anaerobic threshold during celiprolol therapy was 12.3 versus 14.0 ml oxygen/kg per min during placebo administration (a 12% difference, p less than 0.01). Similarly, oxygen uptake at maximal exertion during celiprolol therapy was 17.6 versus 21.0 ml/kg per min during placebo administration (a 16% difference, p less than 0.01). Treadmill time was also reduced during the celiprolol phase compared with placebo (11.3 versus 10.3 minutes; a 19% difference, p less than 0.01). These results indicate that in patients with atrial fibrillation the major beneficial effects of beta-adrenergic blockade--reduced submaximal and maximal exercise heart rate and blood pressure--must be weighed against the decrease in exercise capacity.

Abstract

Nine male patients (mean age 65 yr) with chronic atrial fibrillation underwent maximal exercise testing during placebo, beta-adrenergic (celiprolol, 600 mg), or calcium (diltiazem, 30 or 60 mg four times daily) channel blockade. The results were analyzed to determine which factors most closely related to ratings of perceived exertion (RPE) during exercise. Heart rate (HR), blood pressure (BP), oxygen uptake (VO2), minute ventilation (VE), and carbon dioxide production (VCO2) were evaluated at rest, 3.0 mph/0% grade, the gas exchange anaerobic threshold (ATge), 80% of placebo maximal O2 uptake, and maximal exercise. Both beta-adrenergic and calcium channel blockade significantly reduced heart rate and systolic blood pressure relative to placebo; these effects were more profound during beta-adrenergic blockade and as exercise progressed. Correlation coefficients and estimates of slope were derived for changes in RPE during exercise vs. changes in HR, VO2, VE, and VCO2 during the three treatments (r = 0.76 to 0.92, P less than 0.001). Although RPE was significantly correlated with HR during placebo and diltiazem therapy (r = 0.45, P less than 0.01), this was not the case during beta-adrenergic blockade (r = 0.31, NS). Slope of the regression lines between RPE and VO2, VE, and VCO2 did not differ between the three treatments. Slope of the regression lines between RPE and HR differed only during calcium channel blockade. Because the presence of atrial fibrillation and beta-adrenergic blockade altered the associations between RPE, VO2, and HR, these results suggest that VE is more closely related to RPE than the other parameters.

Abstract

Although changes in lifestyle may increase the life expectancy of persons at high risk for coronary disease, there is no cost-effective screening test that can select these persons from the general population. Exercise testing has been considered, but epidemiologic studies have not proved that it effectively identifies persons at risk for myocardial infarction or cardiac death. Theoretically, exercise testing should have limited sensitivity in predicting events because abnormal responses occur only when sufficient atherosclerotic plaque has accumulated to impede coronary flow. Abnormal test responses cannot occur before plaque has reached such dimensions. A test that indicates the presence of any atherosclerotic plaque in the coronary lumen would be more useful than one that indicates compromise of blood flow. Data show that sensitive detection of coronary calcific deposits accurately predicts the presence of atherosclerotic plaque. Sensitive radiographic techniques such as digital subtraction fluoroscopy need to be developed as screening tests. Screening studies should be blinded and include only hard endpoints, and follow-up periods should be no less than 10 years so that the detected disease can develop to its symptomatic endpoint.

Abstract

To evaluate the influence of an exercise program on spatial and left precordial R-wave amplitude among patients with coronary artery disease, computerized electrocardiogram (ECG) data were acquired during maximal treadmill testing before and after 1 yr in 89 patients randomized to either exercise (n = 40) or control (n = 49) groups. Spatial and lateral R-wave amplitudes were derived from the orthogonal Frank (XYZ) lead system. The exercise group significantly increased maximal O2 consumption (0.17 l/min), whereas controls decreased significantly (0.12 l/min, P less than 0.01 between groups). No significant changes in electrocardiographic R-wave voltage measurements occurred within or between groups during the year. It is concluded that exercise training does not result in increases in R-wave voltage in patients with coronary artery disease.

Abstract

The effect of exercise training on myocardial perfusion was assessed using initial and 1-year thallium-201 (Tl-201) exercise studies in 56 patients with stable coronary artery disease (CAD). Subjects had been randomized into a trained group participating in supervised exercise three times per week and a control group. Indices (non-dimensional units) based on computer-analyzed circumferential count profile from nine regions of the heart, assessed in three projections, were used to eliminate observer bias and more accurately quantitate Tl-201 distribution and 4-hour washout. There was serial improvement of the global distribution count profiles in 21 of 27 (77.8%) of the trained and in 9 of 29 (31.0%) of the control subjects (p less than 0.001). The mean interval change in global initial distribution over the year period was 5 +/- 13 (mean +/- SD) in the trained and -6 +/- 14 in the control groups (p less than 0.003). The mean initial distribution of the trained group had improvement in all nine regions (significant in three), while the control group showed mean improvement in only one of nine regions. Additionally, the trained group showed improvement in the mean washout in five of nine regions (significant in three), while no mean regional washout improvement occurred in the control group. Thus, in this group of patients with stable CAD, exercise training resulted in apparently improved cardiac perfusion evidenced by enhance Tl-201 uptake and washout.

Abstract

Exercise-induced changes in QRS duration were assessed in 25 normal subjects and in 17 patients with stable ischemic heart disease. None had bundle branch block or were taking medications, and all patients had angina pectoris induced during the test. QRS duration and ST60 amplitude were measured by computer during rest while standing, at a heart rate of 100 to 110 bpm during exercise, at peak heart rate for the angina patients (mean of 127 bpm), and at the corresponding matched heart rate and peak heart rate for the normals (mean of 174 bpm). As heart rate increased, the patients showed significant ST60 depression. In normal subjects, the QRS duration tended to increase initially but at the matched heart rate level and at peak heart rate it decreased significantly compared to rest (p less than 0.01). The QRS duration in the angina patients increased significantly at the heart rate level of 100 to 110 bpm (p less than 0.05). Of the eight patients who reached a peak heart rate above 127 bpm, six (75%) during that period further increased QRS duration compared to three (12%) of the 25 normal subjects (p less than 0.001). We conclude that a consistent increase in QRS duration during exercise, although subtle, may be a marker of ischemia and consequently a potential diagnostic tool.

Abstract

This study was performed in order to determine whether exercise-induced myocardial ischemia demonstrated by thallium-201 imaging could be detected by ST segment shifts in patients with abnormal Q waves at rest. Fifty-four patients with coronary artery disease and exercise-induced thallium-201 defects were compared to 22 patients with similar Q wave patterns but without thallium-201 exercise defects and to 14 normal subjects. Exercise data were analyzed visually in the 12-lead ECG and for spatial ST vector shifts. Both ST segment depression observed on the 12-lead ECG and spatial criteria were reasonably sensitive and specific for ischemia when the resting ECG showed no Q waves or inferior Q waves (range 69% to 93%). However, when anterior Q waves were present, ST segment shifts could not distinguish patients with ischemia from those with normal perfusion as determined by thallium imaging.

Abstract

The physiologic results of acute dynamic exercise include complex neurologic, hormonal, pulmonary, and cardiovascular adjustments that provide an integrated response perfectly matching oxygen supply with oxygen demands. Long-term repeated bouts of dynamic exercise of sufficient intensity and duration yield predictable changes in anatomy and physiology. These changes affect active skeletal muscle and the heart. Changes in skeletal muscle include an increased capillary blood volume, increased mitochondrial density, increased oxidative pathway enzymes, and more efficient regulation of blood flow. These adaptations result in an increased oxidative capacity and more favorable fuel utilization. Oxygen extraction increases, accounting for up to 50 per cent of the increased maximal oxygen consumption, and endurance improves. Following chronic dynamic exercise the heart beats slower and has a larger stroke volume at rest and throughout a broad range of work intensities. The maximal cardiac output increases substantially, accounting for up to 50 per cent of the increased maximal oxygen consumption. The metabolic and biochemical changes found in skeletal muscle are not found in cardiac muscle. Changes found in isolated cardiac muscle do not always correlate with heart performance. The separation of central and peripheral factors in assessing heart performance is difficult because preload and afterload are major determinants of heart function and are altered by chronic dynamic exercise. Ischemia is a major stimulus for the development of coronary collateral vessel development in animals. Because dynamic exercise does not induce ischemia in normal humans, collateral vessel development may only occur in those with coronary heart disease. However, there is no convincing evidence that chronic dynamic exercise results in physiologically important coronary collateral vasculature in patients with angina. Improved work capacity is predictable following chronic dynamic exercise in patients with coronary heart disease. Although the rate pressure product that produces angina does not change following training, heart rates are lower at matched absolute workloads and the maximal consumption of oxygen increases. Changes in heart function are largely secondary to peripheral changes in these patients.

Abstract

Fifty-three male volunteers who had undergone coronary artery bypass surgery were randomized to a medically supervised exercise program (N = 28) or to usual community care (N = 25). They were tested initially and at one year with exercise tests for thallium scintigraphy, maximal oxygen uptake, and electrocardiography. Approximately one third of the patients had signs and/or symptoms of ischemia consistent with incomplete or unsuccessful revascularization. Over the year there were five dropouts, but no major complications occurred. The exercisers attended an average of 82% of the sessions (three times a week) and trained at 80% of their maximal heart rate. Both the exercisers with and those without angina had significant increases in estimated and measured oxygen uptake and significant declines in submaximal and resting heart rate. There was a trend toward improved thallium scans in the exercised patients with angina.

Abstract

Sixteen patients with stable angina pectoris were studied in a double blind crossover manner utilizing treadmill exercise testing with the direct measurement of total body oxygen uptake, 1 and 24 hours after application of a 20 cm2 transdermal nitroglycerin system and identical placebo. Testing was performed after a 3 day lead-in period of treatment with either an active patch or placebo. Points of analysis were peak angina and the submaximal work load occurring at 4 minutes of exercise. No statistically significant differences were observed between nitroglycerin and placebo treatment in any of the rest hemodynamic or peak angina variables at 1 or 24 hours. A significant increase in the rate-pressure product at the submaximal work load was observed 1 hour after transdermal nitroglycerin relative to placebo application. However, no significant differences were observed in any of the other measured variables at the submaximal work load, 1 or 24 hours after nitroglycerin application. The once daily application of a 20 cm2 transdermal nitroglycerin system was ineffective in altering the exercise capacity of patients with angina pectoris. The lack of efficacy at 1 hour appears to be due to inadequate nitroglycerin blood levels; at 24 hours it may be due to tolerance.

Abstract

Thirty patients who exhibited increased and 65 patients decreased spatial R wave amplitude during exercise testing were compared for left ventricular function and ischemic variables. Spatial R wave amplitude was derived from the three-dimensional Frank X, Y, Z leads using computerized methods. All patients had stable coronary artery disease and they were classified into two groups: one that attained a higher (n = 48) and one a lower (n = 47) median value of maximal heart rate during exercise (161 beats/min). Within these two groups, patients with increasing or decreasing spatial R wave amplitude during exercise were analyzed for differences in oxygen consumption, exercise-induced changes in spatial R wave amplitude, ST segment depression laterally (ST60, lead X), ST displacement spatially, left ventricular ejection fraction at rest, change in left ventricular ejection fraction with exercise and thallium-201 ischemia during exercise. Significant differences were demonstrated only in exercise-induced spatial R wave amplitude changes (p less than 0.0001). There was no significant correlation between exercise-induced change in heart rate and change in spatial R wave amplitude in either the group with increasing or the group with decreasing spatial R wave amplitude. It is concluded that changes in spatial R wave amplitude during exercise are not related to ischemic electrocardiographic or thallium-201 imaging changes or to left ventricular ejection fraction determined at rest or during exercise.

USE OF CLINICAL-DATA IN PREDICTING IMPROVEMENT IN EXERCISE CAPACITY AFTER CARDIAC REHABILITATIONJOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGYHammond, H. K., Kelly, T. L., Froelicher, V. F., Pewen, W.1985; 6 (1): 19-26

Abstract

Fifty-nine men with coronary heart disease underwent 1 year of supervised aerobic exercise. They performed exercise tests for maximal oxygen uptake, ST segment analysis, thallium scintigraphy and radionuclide ventriculography before and after the year of exercise. A computerized data base that included clinical descriptors and exercise test results was retrospectively reviewed to determine whether initial features could predict the patient's response to the exercise intervention. Poor correlations were found between the initial measurements and change in maximal oxygen consumption and other indexes of training effect. Patients who initially were in the poorest state of fitness showed the most improvement with training. None of the initial features from the history and physical examination, treadmill study or radionuclide studies was a good predictor of a beneficial result from the exercise program. The usual measurements of work intensity during training were poor predictors of outcome. A significant decrease in the amount of ischemia measured by thallium perfusion scintigraphy was demonstrated after training.

NONINVASIVE TESTING IN THE EVALUATION OF MYOCARDIAL ISCHEMIA - AGREEMENT AMONG TESTSJOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGYHammond, H. K., Kelly, T. L., Froelicher, V. F.1985; 5 (1): 59-69

Abstract

The purpose of this study was to investigate the relations among four exercise-induced phenomena--angina, ST segment depression, decrease in ejection fraction and thallium perfusion defects--and to determine their impact on aerobic capacity. One hundred fifty-six men (mean age 52 +/- 8 years) with documented coronary heart disease were studied with radionuclide ventriculography during supine bicycle exercise, thallium scintigraphy and treadmill testing with computerized electrocardiography and maximal oxygen uptake. Of 624 administered tests, 243 results (39%) were considered to indicate ischemia. The average number of abnormal tests was 1.6 per patient and, when considered as continuous variables, their results correlated poorly. Correlations did not improve when adjusting for heart rate achieved or by eliminating patients with coronary artery bypass surgery or myocardial infarction. Statistical methods of comparing degree of interest agreement yielded surprisingly weak relations among the four tests of ischemia. Treadmill performance was markedly impaired by angina, but much less impaired by other indicators of ischemia. It is concluded that the usual test responses implying ischemia have weak agreement when uniformly applied to patients with known coronary artery disease.

Abstract

Out of 156 patients with stable coronary heart disease randomized to either an exercise intervention group or a control group, 41 had complete gas analysis data. Continuous gas exchange data, including the ventilatory threshold, and selected heart rates were determined initially and at 1 year. The mean attendance for the exercise group was 2.2 +/- 0.7 days a week at an intensity of 60 +/- 9% of estimated peak oxygen uptake for 1 year of the study. Statistically significant differences (p less than 0.05) were observed between the exercise group (n = 19) and the control group (n = 22) for peak oxygen uptake (L/min), total treadmill time, and supine rest and submaximal heart rates after 1 year. The most remarkable change was a 16% increase in treadmill time. There was no difference between groups for the ventilatory threshold expressed either as an absolute oxygen uptake or as a percentage of peak oxygen uptake at 1 year. However, there was a significant correlation (r = 0.45; p less than 0.05) between the absolute change in peak oxygen uptake and the absolute change in the ventilatory threshold. These results indicate that a moderate exercise program is inadequate to alter the ventilatory threshold in patients with coronary heart disease and that changes in ventilatory threshold do not explain the increase in treadmill time that usually occurs.

Abstract

To determine the individual reproducibility of radionuclide ventriculography over an extended period of time, 33 patients with stable coronary artery disease were studied at rest and during three stages of exercise on two occasions separated by 1 year. The individual interstudy variability of ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume, and cardiac output was determined by calculating the mean and standard deviation of the difference between the individual studies (initial - 1 year). Despite high correlations between an EF measured at study 1 and study 2 of 0.96 at rest and 0.87 during maximal exercise, the individual interstudy difference was 0.01 +/- 0.04 and -0.02 +/- 0.09, respectively. The correlation of percent change in EF from rest to maximal exercise was 0.49 and the individual interstudy differences was -1.2 +/- 19%. Correlations of the EDV were 0.81 at rest and 0.72 during maximal exercise while the individual difference was 0.7 +/- 38 and -0.8 +/- 49 ml, respectively. Considering two standard deviations as the confidence limits for a true change, an EF change of 8 EF units (0.08) at rest and 18 (0.18) during exercise, and EDV changes of approximately 100 ml are needed in an individual to state with confidence that the observed difference between the two studies are true changes and not the result of technologic variability. Because of the large individual interstudy variability in EF and volume measurement, caution must be taken in assuming that any change over a year is due to more than technique variability.

Abstract

In order to determine the effect of electrode placement and standing on the 12-lead electrocardiogram required prior to exercise testing, 104 male patients with stable coronary heart disease were studied. Electrocardiograms were recorded with two different placements of the arm electrodes commonly used for exercise testing with the patient supine and standing. These were compared to a standard ECG with the electrodes placed at the wrists and ankles with the patient supine. The four ECGs gathered on each patient were analyzed using standard visual techniques for diagnostic changes and using a computer for analysis of axis, amplitudes, and durations. There were important differences between the standard 12-lead ECG and the ECGs gathered with the pre-exercise test modifications. These differences were minimized by placing the arm electrodes as close to the shoulders as possible and by recording the ECG with the patient supine.

Abstract

Fourteen male patients with exercise test-induced angina and ST-segment depression underwent treadmill testing on three consecutive days to evaluate the reproducibility of certain treadmill variables. Computerized ST-segment analysis and expired gas analysis, including anaerobic threshold, were evaluated for reproducibility using an intra-class correlation coefficient analysis. Measured oxygen uptake at peak exercise displayed better reproducibility than total treadmill time, the onset of angina, and the gas exchange anaerobic threshold (ATGE). The double product, heart rate, and ST-segment displacement in lead X were found to be reproducible at peak exercise, the onset of angina, and the ATGE. The incorporation of gas exchange analysis can provide accurate physiologic determinants of exercise capacity in patients with angina pectoris. In addition, noninvasive estimates of myocardial oxygen demand and ischemia can be reproducibly determined. These findings have important implications for the design of studies evaluating the effects of an intervention on angina pectoris.

A RANDOMIZED TRIAL OF THE EFFECTS OF 1 YEAR OF EXERCISE TRAINING ON COMPUTER-MEASURED ST SEGMENT DISPLACEMENT IN PATIENTS WITH CORONARY-ARTERY DISEASEJOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGYMyers, J., Ahnve, S., Froelicher, V., Livingston, M., Jensen, D., Abramson, I., Sullivan, M., Mortara, D.1984; 4 (6): 1094-1102

Abstract

As part of a randomized trial of the effects of 1 year of exercise training on patients with stable coronary artery disease, 48 patients who exercised and 59 control patients had computerized exercise electrocardiography performed initially and 1 year later. The patients who had exercise training as an intervention had a 9% increase in measured maximal oxygen consumption and significant decreases in heart rate at rest and during submaximal exercise. ST segment displacement was analyzed 60 ms after the end of the QRS complex in the three-dimensional X, Y and Z leads and utilizing the spatial amplitude derived from them. Statistical analysis by t testing yielded no significant differences between the groups except for less ST segment displacement at a matched work load, but this could be explained by a lowered heart rate. Analysis of variance yielded some minor differences within clinical subgroups, particularly in the spatial analysis. Obvious changes in exercise-induced ST segment depression could not be demonstrated in this heterogeneous group of selected volunteers with coronary artery disease secondary to an exercise program.

Abstract

In order to determine whether areas of ischemia identified by thallium-201 scintigraphy could be localized by exercise ECG, we studied 54 patients with stable coronary heart disease. All 54 patients had exercise-induced thallium-201 scintigraphic defects. Their exercise ECG test results were compared to their thallium-201 images and also to 14 low-risk normal subjects. Exercise data were analyzed for spatial ST vector shifts, using a computer program in order to most accurately classify ST segment depression and elevation. Thallium-201 ischemic defects detected in our patients included areas in the septum and the inferior, lateral, and anterior walls. Twenty-six of these 54 patients also had coronary angiography for classification and comparison as having either localized or generalized disease. None of the scintigraphic ischemic sites or angiographic diseased areas could be specifically identified by exercise-induced ST vector shifts. Therefore, the surface exercise ECG has limitations in localizing ischemia to specific areas of the myocardium.

Abstract

In order to determine whether or not regular exercise could alter myocardial perfusion or function, we randomized 146 male volunteers with stable coronary heart disease to either a supervised exercise program (n = 72) or to a usual care program (n = 74). Subjects underwent exercise tests initially and one year later. Significant differences between the two groups included improved aerobic capacity, thallium ischemia scores, and ventricular function in the exercise intervention group. It was not possible to classify the conditions of patients as to the likelihood of improvement or deterioration. This study demonstrated changes in myocardial perfusion and function in a select group of middle-aged men with coronary heart disease who underwent a medically appropriate exercise program lasting one year, but these changes were relatively modest.

Abstract

To investigate the cardiac determinants of treadmill performance in patients able to exercise to volitional fatigue, 88 patients with coronary heart disease free of angina pectoris were tested. The exercise tests included supine bicycle radionuclide ventriculography, thallium scintigraphy and treadmill testing with expired gas analysis. The number of abnormal Q wave locations, ejection fraction, end-diastolic volume, cardiac output, exercise-induced ST segment depression and thallium scar and ischemia scores were the cardiac variables considered. Rest and exercise ejection fractions were highly correlated to thallium scar score (r = -0.72 to -0.75, p less than 0.001), but not to maximal oxygen consumption (r = 0.19 to 0.25, p less than 0.05). Fifty-five percent of the variability in predicting treadmill time or estimated maximal oxygen consumption was explained by treadmill test-induced change in heart rate (39%), thallium ischemia score (12%) and cardiac output at rest (4%). The change in heart rate induced by the treadmill test explained only 27% of the variability in measured maximal oxygen consumption. Myocardial damage predicted ejection fraction at rest and the ability to increase heart rate with treadmill exercise appeared as an essential component of exercise capacity. Exercise capacity was only minimally affected by asymptomatic ischemia and was relatively independent of ventricular function.

Abstract

The best available assessment of aerobic capacity is measurement of the consumption of oxygen at maximal dynamic effort. When carefully administered, this measurement is remarkably reproducible. Major sources of error in obtaining this measurement include improper gas collection apparatus, inaccurate flow meters, and failure to correct for water pressure in the expired gas. Obtaining a truly maximal effort in an objective manner is also a major limitation. The protocol used in the measurement is of minor importance although treadmill testing usually gives higher values than stationary bicycling. The cost and inconvenience of direct methods of measurement have made indirect methods attractive; however, these methods give less accurate quantifications of aerobic capacity and are not as useful to the athlete interested in gauging his or her improvement following a chronic exercise programme. Extrapolating data obtained from the laboratory to performance in specific athletic endeavours is tenuous. Of course, elite marathon runners will have high maximal oxygen consumption. But one cannot accurately predict how individual athletes will perform in their events; these measurements do not account for the psychological component so important in athletic performance. Perhaps the best use of the measurement of maximal oxygen consumption in athletes is in assessing the success of training programmes in a longitudinal manner.

Abstract

In order to evaluate the clinical practice of estimating oxygen uptake from treadmill time, patients with coronary heart disease and normal subjects had their oxygen uptake measured during treadmill testing. Continuous expired gas analysis was performed in order to see if the gas exchange anaerobic threshold could explain the difference between measured and estimated oxygen uptake. Below the gas exchange anaerobic threshold, normal subjects and patients had similar oxygen uptakes for a given workload. However, at workloads above this threshold, patients had approximately 1 MET lower oxygen uptake than normal subjects. Regression equations relating treadmill time to oxygen uptake are specific to groups of patients or individuals due to differences in anaerobic threshold. In addition, the use of standard workloads to predict aerobic capacity depends on the rate at which oxygen uptake obtains a steady state value. These findings must be considered in clinical practice when attempting to estimate aerobic capacity from treadmill testing.

Abstract

A lower than normal heart rate response to maximal dynamic exercise, known as chronotropic incompetence or heart rate impairment, has been demonstrated to have a poor prognosis. In order to better describe patients with this finding, 156 men with coronary heart disease were evaluated. All patients were studied with maximal exercise testing, including measurements of oxygen consumption, exercise electrocardiograms, thallium scintigraphy and radionuclide ventriculography. Chronotropic incompetence was defined as a maximal heart rate 1 standard error of the estimate below the regression line of age versus maximal heart rate on two separate exercise tests. In patients so defined, mean maximal oxygen consumption was significantly lowered and angina was the major reason for stopping exercise on the treadmill. Patients with chronotropic incompetence not limited by angina had more evidence of myocardial scar and dysfunction and had a greater prevalence of three vessel coronary disease than did patients with a normal heart rate response. Radionuclide testing results suggest that among patients with chronotropic incompetence, those with angina have a better prognosis than those who do not have angina but who may have myocardial dysfunction.

SCREENING FOR ASYMPTOMATIC CORONARY-ARTERY DISEASEJOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGYUHL, G. S., Froelicher, V.1983; 1 (3): 946-955

Abstract

Because it will be some time before the primary prevention of cardiovascular disease is a reality, it is advisable to evaluate screening methods for detecting latent cardiovascular disease. Because risk factor screening and techniques with the patient at rest have limited sensitivity, exercise testing that brings out abnormalities not present at rest deserves consideration. Numerous studies have shown the exercise electrocardiogram to have a sensitivity of approximately 50% and a specificity of 90%. The different reported predictive values are related to its use in populations with different prevalences of disease. Various techniques have been recommended to improve the sensitivity and specificity of exercise testing, including other exercise measurements, computerized probability estimates, nuclear cardiology, cardiokymography, cardiac fluoroscopy and risk factor analysis. There is promise that these techniques will improve attempts to screen asymptomatic subjects for coronary disease.

Abstract

Four electrocardiographic scoring systems for the assessment of left ventricular function or presence of myocardial infarction were evaluated in 231 patients with coronary artery disease. Electrocardiographic scores were compared with radionuclide ejection fraction and thallium perfusion studies. The correlation between Wagner's modified QRS score and ejection fraction was only fair (r = -0.60). Askenazi's sum of R wave voltage score correlated poorly with ejection fraction (r = 0.44), as did Gottwik's sum of voltage score from the Frank lead electrocardiogram (r = 0.44). Rautaharju's Cardiac Infarction Injury Score did not reliably predict presence of infarction in the patient group, nor did it correlate well with ejection fraction (r = -0.49). None of the correlations were significantly improved when only patients with a history of a myocardial infarction, a thallium defect compatible with a scar or a diagnostic Q wave were considered. Although Wagner's QRS score correlated best with ejection fraction, all scoring systems had limited clinical usefulness for estimating ejection fraction.

Abstract

In order to evaluate computerized methods of electrocardiographic signal processing, determination of QRS end, and measurement of criteria for ischemia, we analyzed the data from 42 male patients with coronary heart disease who underwent maximal treadmill testing. Electrocardiographic data were digitized on-line and leads X, V5, Y and Eigen V were later analyzed for noise content, isoelectric baseline, and ST parameters using the UCSD spatial electrocardiographic computer program. Various ST segment criteria for ischemia were calculated and compared. Noise was greater in lead Y and in all leads when the median was used for signal averaging. Two isoelectric baseline algorithms and three ST segment slope algorithms gave similar results. Spatially derived QRS end was highly correlated with the amplitude measured using a fixed time interval after peak R wave. Both ST area and ST midpoint estimates differed widely using two different algorithms for each. Regression equations were derived that make it possible to estimate QRS end or ST60 amplitudes in V5 from values in X or vice versa.

EXERCISE TESTING AND TRAINING - CLINICAL-APPLICATIONSJOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGYFroelicher, V. F.1983; 1 (1): 114-125

Abstract

The application of exercise in clinical cardiology continues to progress because of research findings. Advances have occurred in the applications, methodology and interpretation of exercise testing. Exercise training has been documented to have a place in the primary prevention of coronary heart disease. In regard to cardiac rehabilitation, both early ambulation and early discharge are safe and beneficial in patients with uncomplicated infarction, and a subsequent exercise program is at least as effective as other interventions. High intensity exercise training in the patient with heart disease may be necessary to cause changes in myocardial perfusion and performance, but it carries an increased risk.

Abstract

The efficacy and safety of atenolol was evaluated in 16 patients with exertional angina pectoris in a single-blind, once daily, increasing dose study. All patients had coronary artery disease documented by previous myocardial infarction, coronary angiography, or an abnormal exercise ECG. After a four-week placebo period, patients received 25, 50, and 100 mg of atenolol once daily during three two-week periods. This was followed by a three-week treatment period with 200 mg of atenolol once daily. The study was concluded with a two to four week posttreatment period. Antianginal efficacy was assessed by monitoring changes in treadmill exercise performance in each patient 3 and 24 hours after the administration of atenolol. The endpoint of the treadmill exercise was mild but definite chest pain. At 3 and 24 hours after all dosages, atenolol significantly prolonged the duration of exercise and increased the work performed. The pulse rate and double product at the endpoint of exercise were lower with all atenolol doses. Overall, at 24 hours after the administration of atenolol, exercise tolerance was progressively increased as the dose increased. The mean duration of exercise and work performed increased 28.5 and 35.4%, respectively, on the 25-mg dose; 36.9 and 45.5%, respectively, on the 50-mg dose; 45.1 and 59.5%, respectively, on the 100-mg dose; and 65.4 and 84.8%, respectively, on the 200-mg dose. Patient acceptance and compliance were good. Single daily doses of atenolol constitute effective therapy for exercise-induced angina.

Abstract

A computerized method of acquiring and analyzing rest and exercise test 12-lead electrocardiographic and three-dimensional lead vectorcardiographic data before and after cardiac rehabilitations is described. Fourteen coronary heart disease patients were exercise tested before and after a mean of five months of aerobic exercise training, The only significant ST-segment improvements were found in three-dimensional space. Spatial measurements should be considered in the assessment of electrocardiographic changes secondary to exercise training.

Abstract

Seventeen coronary patients (CAD) underwent thallium (TI-201) treadmill and radionuclide (RNV) ejection fraction supine bicycle testing before and after 5.6 +/- 1.6 (mean +/- SD) months of an exercise program. Thallium data were assessed both using analog images and a computerized circumferential profile technique. Patients exercised on the treadmill to a higher workload after the exercise program, but achieved a similar pressure-rate product. When interpreting the analog thallium images, only 50% agreement was obtained for the assessment of changes in myocardial perfusion (pre/post-training). The computer technique, however, had low inter-intraobserver variability (6%) and better agreement (90.5%). Using the circumferential profile method, five patients improved (a total of 11 regions) and one patient worsened (with two regions). Before the exercise program, the ejection fraction (EF) response to supine bike exercise was normal (an increase greater than 11%) in four, flat in seven, and severely abnormal (a decrease of more than 4%) in six patients. After the exercise program, even though achieving similar or higher pressure-rate products, six patients improved their EF response, nine did not change, and two worsened. Of the five patients who improved their thallium images, one improved his EF response, two remained normal, and two did not change. One patient worsened both his thallium study and the EF response after the exercise program. Changes in thallium exercise images and the EF response to supine exercise occurred in our patients after an exercise program, but were not always concordant. Indeed, of five patients with exercise-induced ischemic ST changes before and after training, the EF response improved in three whereas myocardial perfusion was unchanged. Reasons for this lack of agreement are discussed, and have been considered in the planning of a randomized trial of the effects of an exercise program on myocardial perfusion and function.

Abstract

The rest and exercise ECG, 201thallium myocardial scintigram (201T1), and radionuclide ventriculography are noninvasive procedures which can be used to evaluate myocardial damage and ischemia. To compare these procedures and to obtain baseline information, 85 male patients with coronary heart disease were evaluated prior to beginning an exercise program. Findings at rest included Q waves or bundle branch block in 54%; 47% had 201T1 redistribution defects and 33% an abnormal ejection fraction (EF). Of the 39 patients with normal ECGs, 31 had no 201T1 defects and only of these 31 (3%) had an abnormal EF. Abnormal EF or 201T1 redistribution defects did not occur in patients without a history of myocardial infarction. Abnormal resting EF occurred in 63% of patients with abnormal versus 7% of those with normal 201T1 redistribution scans. Exercise test results included an abnormal ST-segment response in 80%, an abnormal EF response in 65%, and a 201T1 ischemic defect in 37%. Twenty patients had exercise-induced ST elevation, and this phenomenon was more related to ventricular aneurysms than to ischemia. 201Thallium imaging, radionuclide ventriculography, and the ECG provide results regarding myocardial damage that agree by more than chance, while the exercise induced ST-segment changes did not agree with the radionuclide indications of exercise-induced ischemia.

Abstract

The potential advantages of digital computer processing of exercise electrocardiographic data include reduction of noise, compression of data, improved precision and application of optimal criteria. Most prior approaches to such processing required equipment that was both expensive and inconvenient. With the revolution in instrumentation brought about by the development of microcomputers, powerful dedicated computers can now be afforded by many exercise laboratories. There are many approaches to computerized management of exercise electrocardiographic data and various criteria for ischemia. Studies are necessary to validate computer algorithms so that these devices can be used diagnostically to best advantage. Cardiologists need some understanding of this field so that they can be discriminating users of computer systems. In addition, the results of studies correlating electrocardiographic changes with radionuclide methods of assessing myocardial perfusion and function should enable such assessments to be made from the electrocardiographic signals alone, particularly when aided by computer analysis of spatial shifts.

Abstract

Studies have shown that the number of high-frequency QRS notches increases after myocardial infarction (MI). To assess overall high-frequency (greater than 80 Hz) potentials more quantitatively, we adapted filtered and the root-mean-square (RMS) voltage of the residual (80-300 Hz) signal computed. High-frequency RMS values were significantly (p less than 0.01) greater in leads II, III and aVf in normal subjects (n = 12) than in patients with inferior infarction (n = 12). Similarly, high-frequency RMS values were higher (p less than 0.01) in leads V2 and V5 in normal subjects (n = 14) than in patients with prior anterior MI (n = 14). A reduction in high-frequency RMS values with inferior infarction was independently confirmed using Fourier analysis of the QRS in lead II. QRS notching in these subjects was also quantified by computing the number of baseline crossings of the first derivative (dV/dt). As predicted, notching was significantly greater (p less than 0.05) both with inferior MI (lead II) and anterior MI (lead V5). However, contrary to classic theory, the number of notches correlated negatively with direct measurements of high-frequency RMS voltage in lead II (r = -0.63) and lead V5 (r = -0.49). Positive correlations were obtained between high-frequency potentials and two new indexes that measure the amplitude of QRS dV/dt-peak-to-peak amplitude of dV/dt and RMS dV/dt. Using these indexes, absolute separation of inferior MI patients and normal subjects was obtained. We conclude that MI increases low-amplitude QRS notching but diminishes total high-frequency voltage, probably because of an overall decrease in electromotive potentials and slowing of ventricular conduction.

Abstract

To determine whether exercise training results in increased left ventricular mass in patients with ischemic heart disease, we obtained echocardiograms in 14 coronary patients before and after an average of seven months (range 3 to 14 months) of supervised arm and leg exercise. Each echocardiogram was interpreted jointly by two blinded observers, using three different measurement conventions and a semiautomated method of analysis to minimize errors of interpretation. Exercise training led to subjective improvement in all 14 patients, and to an objective increase in functional capacity in 13 of 14 patients, as evidenced by an increase in maximal oxygen consumption estimated from symptom-limited treadmill exercise testing (8.8 +/- 2.7 (SD) and 10.7 +/- 2.5 METS before and after training, respectively, p less than 0.01). However, this functional improvement was not accompanied by any significant change in left ventricular end-diastolic diameter, or posterior wall or interventricular septal thickness. Likewise, left ventricular cross-sectional area (CSA), an index of left ventricular mass which corrects for altered ventricular volume and theoretically reflects directional changes in mass despite nonuniform wall thickness, did not change significantly after training by any measurement convention (CSA = 18.0 +/- 6.5 and 17.6 +/- 6.5 cm2 before and after training, respectively, by American Society of Echocardiography measurements). These data strongly suggest that improved functional capacity after exercise training in patients with ischemic heart disease is not due to exercise-induced left ventricular hypertrophy.

Abstract

To assess the agreement of human interpretation of analog thallium myocardial perfusion images, four experienced interpreters evaluated 100 images on two occasions using a form designed to limit reader variability. A high intraobserver agreement (agreement by same observer at separate times) of 89--93% was found when films were interpreted as normal or abnormal (a dichotomous decision). Interobserver agreement for a majority grouping of observers (three or four) was 75% for an abnormal and 68% for a normal interpretation. However, agreement ranged from 11--79% when interpreters were asked to read the anatomic location of defects. Posterior and lateral wall defects were interpreted with the least amount of agreement. These results indicate that caution must be taken when interpreting defect location. Using a scale of 1--10 to grade the severity of a defect, correlations of 0.82--0.86 were found when reading defects in the lateral and anterior projections. Higher correlations, from 0.86--0.94, were found in left anterior oblique views. Use of reporting forms with specific criteria, multiple observers at one occasion, and/or computer processing may improve agreement. A brief review of the agreement of cardiology testing procedures is also presented.

Abstract

Forty healthy young men at low risk for coronary artery disease underwent progressive maximal treadmill testing. Four bipolar electrocardiographic leads including CM5, CC5, inferior-superior Y, anterior-posterior Z, and a standard V5 were recorded and later computer-processed. Measurements included amplitudes of the Q, R, S, J junction and T wave, R-T and Q-S intervals and S-T segment slope. These variables are presented as the 10th, 50th (median) and 90th percentiles throughout the testing procedure to define reference values for the electrocardiographic response to maximal treadmill testing. The medians are presented graphically so that the exercise-induced changes can be visualized. In addition, the percent change of R wave amplitude in V5 compared with the supine pretest value is displayed for each subject during and after testing.

Abstract

The mechanism for R wave amplitude changes during exercise testing is controversial. To investigate this, we recorded vectorcardiograms (VCG) during supine rest and bicycle exercise in 13 normals and 33 patients with coronary heart disease. In all normals, and in those CHD patients with an exercise-induced decrease in R wave amplitude, there was a posterior shift of the QRS vector loop in the transverse plane. In the CHD patients with an increase or no change in R wave amplitude, there was an anterior shift of the QRS vector loop. Though spatial vector length decreased with exercise and correlated with R wave changes, there was a better correlation between changes in the maximal QRS vector angle and R wave amplitude. The etiology of R wave changes during exercise appears to be mainly due to shifts in QRS vector loops, but the reason for these shifts is unknown.

Abstract

Studies based on analysis of QRS notching and slurring have suggested an increase in high frequency QRS potentials following myocardial infarction (MI). We investigated the sensitivity and specificity of an indirect, but easily quantitated index of high frequency potentials--the peak-to-peak amplitude of the high frequency signal. A commercially-available micro-processor ECG system was employed with a QRS-averaging program to reduce random noise and an 80-300 Hz filter to selectively record higher frequency potentials. High frequency ECGs were recorded in leads II, III and aVF in 40 normal men and 41 patients with prior inferior MI. Peak-to-peak amplitude of the high frequency signal was less than or equal to 35 micro V in one or more of these leads in 18 of 41 MI patients (44%) compared with only 1 of 40 normals (2.5%) (P < 0.001). In the infarct group, reduced peak amplitude of the high frequency signal was also noted in some leads where the standard ECG did not show pathologic Q waves. This diminution in peak amplitude probably reflects a reduction in high frequency voltage. Therefore, contrary to previous theory, MI may actually cause a decrease in high frequency potentials as part of an overall loss of electromotive force or a slowing of conduction associated with myocardial necrosis. Quantitative high frequency QRS measurements may be of critical value in selected cases.

Abstract

Improvement in cardiac perfusion has not been demonstrated in man to explain the increased functional capacity secondary to exercise training. Thallium imaging is a noninvasive method of evaluating myocardial perfusion and scaring. Therefore, using thallium exercise tests, we studied 17 patients with coronary heart disease before and after a mean of 6 months participation in cardiac rehabilitation program emphasizing exercise training. Interobserver variability in imaging interpretation was considered by reading images blinded both individually and in consensus. Agreement with defects called by consensus occurred at least 51% of the time individually and normal readings agreed at least 90% of the time. By consensus reading, seven patients showed improved perfusion, seven showed no change, and three worsened following training. Our study shows that thallium scans may be used to demonstrate central changes in myocardial perfusion after cardiac rehabilitation, but larger controlled studies considering redistribution and utilizing image enhancement are necessary to see if such changes are truly secondary to this intervention.

Abstract

Sixteen patients with coronary heart disease (CHD) were studied with rest and exercise thallium scans and gated radionuclide ventriculography before and after 3 to 12 months of exercise training. The 5 patients presented in this report showed improvement in both the ejection fraction and exercise thallium images after training while achieving a higher maximal workload and an equivalent double product. These radionuclide techniques have provided the 1st documentation of improvement in both myocardial perfusion and function in CHD patients after exercise training. A controlled study using advances in imaging technology with patients matched according to postmyocardial infarction time and by the severity of disease is underway to confirm these findings.

Abstract

A heterogeneous group of 19 consecutive patients with coronary artery disease were studied with radionuclide ventriculography before and after a mean of 6 months of exercise training. Ejection fraction was measured at rest, at matched submaximal supine work loads and during maximal supine bicycle exercise. After training there was no change in mean ejection fraction at rest or during maximal exercise, but a higher maximal mean systolic blood pressure, heart rate and work load were achieved. At equivalent submaximal work loads after training, similar levels of mean heart rate and systolic blood pressure were reached but a statistically greater mean ejection fraction was obtained. These preliminary results suggest that exercise training may improve cardiac function during exercise in selected patients with coronary disease. A randomized study using similar techniques has been initiated.

Abstract

To compare two methods of evaluating patients with coronary artery disease, the authors assessed the ejection fraction (EF) during the first-third (1/3) of systole by first-pass radionuclide angiography and the EF response to exercise in 22 normal individuals and 40 patients. The 1/3 EF was calculated by averaging 3--5 beats on the time--activity curve. Exercise EFs were obtained by gated cardiac imaging. The results are shown below, including the per cent change in EF with exercise (% EF). (Formula: see text) p less than 0.05 vs. normals; p less than 0.001 vs. normals; all results are +/- SD. Thirty per cent of patients had a depressed EF, 98% had a depressed 1/3 EF, and 88% had an abnormal EF response to exercise. It is concluded that the 1/3 EF by first-pass radionuclide angiography at rest may be at least as sensitive in identifying patients with coronary artery disease as the EF response to exercise.

AN INTRODUCTION TO THE APPLICATIONS, METHODOLOGY AND INTERPRETATION OF EXERCISE ELECTROCARDIOGRAPHYCARDIOLOGYFroelicher, V. F.1980; 66 (4): 223-235

Abstract

Exercise testing is a very valuable tool in clinical practice since it has many applications including diagnosis, screening, evaluating treatment and for the determination of prognosis and severity of disease. Its methodology has been varied but comparisons of methodology have been performed that make it possible to obtain comparable information from almost any method of testing. The addition of microprocessors to medical instrumentation and the use of nuclear imaging can improve exercise testing. Exercise testing also play an important role in cardiac rehabilitation and in the prescription of exercise for apparently healthy individuals.

Abstract

This review deals with more recent investigations of the health benefit of regular aerobic exercise including studies in: epidemiology, echocardiography, animal research, and cardiac rehabilitation. Recent epidemiological studies support the preventative aspects of exercise in apparently healthy individuals. Echocardiographic studies suggest morphologic changes in young individuals. Recent animal research confirms previous results as well as documenting improvment in cardiac function even under hypoxic and ischemic conditions. Studies of cardiac rehabilitation suggest that medically supervised programs do not improve or worsen morbidity and mortality. The question of whether exercise training can cause cardiac effects in patients with coronary disease rather than just improve the response of the peripheral circulation to exercise may be answered using newer radionuclide techniques.

Abstract

A conscious animal model was developed in which coronary stenosis could be produced while regional myocardial function and local surface electrocardiograms were measured. Responses to isoprenaline stress in the presence of mild (latent) coronary stenosis were then examined. In the absence of coronary stenosis, isoprenaline produced increases in regional function and no change in the surface VCG; at higher doses, increases in the endocardial ST segments occurred. After partial coronary stenosis, which produced no apparent regional dysfunction or electrocardiographic changes, isoprenaline infusion for 3 min (0.02 microgram . kg-1 . min-1) rapidly produced decreases in percentage wall thickening (average 17 +/- 4%, mean +/- SE, P < 0.01) and increases in the mean sum of VCG ST segments by 0.23 +/- 0.06 mV (P < 0.05). 1 min after stopping isoprenaline, most dogs showed further significant deterioration of both measures of ischaemia, but by 5 min there was no significant mean change from control. We conclude that in the presence of latent partial coronary stenosis, stress due to mild sympathomimetic stimulation alone can rapidly induce regional myocardial ischaemia. Deterioration of regional myocardial contractile function during such stress can provide as sensitive means of detecting latent coronary obstruction.

Abstract

New studies support a lifestyle of regular physical activity. Regular physical activity most likely decreases one's risk for coronary heart disease and helps to decrease other risk factors. The inclusion of regular moderate exercise in one's life-style makes good sense for many reasons. It can improve the quality of life by avoiding illness and the quality is definitely improved in those in whom physical performance is important. Some say that physical exercise will increase the quantity of life but the extra years gained are spent exercising.

Abstract

Over 600 fliers have had coronary angiography at the USAF School of Aerospace Medicine since 1971. This paper concerns the incidence of complications, long- and short-term, on the first 463. Information on short-term complications was compiled from computerized data storage and included all 463 patients. Mean age of patients was 40.5 with a range of 22-57 years. Information about long-term complications was obtained from 357 respondents to a three-page questionnaire (77% return rate). Most frequent indication for angiography was an abnormal treadmill stress test, and more than 90% of the patients were asymptomatic. There was no short-term mortality. Nine individuals reported some residual complaints involving the hand, but had no job or physical activity limitation from the procedure. The local arterial complications were more frequent with brachial cutdown than with the femoral percutaneous approach, but the difference in frequency was not statistically significant.

Abstract

In order to describe exercise-induced changes of left ventricular function in patients with atypical chest pain and to determine the diagnosis accuracy of radionuclide angiography in the differential diagnosis of various chest pain syndromes, we studied a consecutive series of 26 patients and 20 healthy volunteers. Only patients with ejection fractions > 0.50 at rest, without antianginal therapy and without a prior myocardial infarction who eventually underwent diagnostic left heart catheterization were included in the study. In all healthy volunteers ejection fraction increased during exercise by at least 10% over the resting level (from 0.61 +/- 0.05 to 0.76 +/- 0.07; P < 0.001). A similar ejection fraction response was found in 14 of the 26 patients (group A): ejection fraction increased from 0.60 +/- 0.06 to 0.72 +/- 0.07 (P < 0.001), whereas in the remaining 12 patients (group B) ejection fraction decreased from 0.62 +/- 0.06 to 0.57 +/- 0.07 (P < 0.01). Left heart catheterization revealed normal coronary arteries in 13/14 group-A patients while 10/12 group-B patients had significant coronary artery lesions (> 50%). The other two group-B patients were found to have idiopathic cardiomyopathies. We conclude that normal subjects with atypical chest pain during exercise have a normal ejection fraction response to exercise despite their symptoms and that therefore radionuclide angiography during exercise is a valuable noninvasive method in the differential diagnosis of exercise-induced chest pain syndromes.

Abstract

The results of rest and exercise ECG, 201Tl myocardial perfusion imaging and equilibrium radionuclide angiography were analyzed in 71 consecutive patients referred for diagnosis or evaluation of coronary artery disease (CAD). In 45 patients the diagnosis was established either by catheterization or typical history. In this group the overall sensitivity for rest/exercise ECG was 66%, for 201Tl scans 74%, for both combined 79% and for the ejection fraction response to exercise determined by radionuclide angiography 97%. If only the exercise response was considered, the corresponding sensitivity values were 58% (ECG), 50% (201Tl scans), 71% (ECG + 201Tl) and 97% (radionuclide angiography). The specificity for coronary artery disease was determined to be 71% for ECG, 86% for 201Tl scans and 42% for radionuclide angiography. All patients with false-positive results by radionuclide angiography had cardiomyopathies, thus this test has a high specificity for left ventricular dysfunction rather than for CAD alone. Criteria developed from the analysis of the test results in the 45 patients with definite diagnoses were then applied to the evaluation of 26 additional patients with atypical chest pain. A diagnosis could be made in all but 5 of them and radionuclide angiography was again the single most reliable test. Based on this study a new approach for the noninvasive evaluation of patients with suspected coronary artery disease is proposed.

Abstract

This paper presents the profiles of left ventricular ejection fraction (EF) during and following supine bicycle exercise in normal subjects and in patients with coronary heart disease, as well as the relationship of the described patterns to clinical parameters. Twenty normal men and 40 patients with coronary artery disease were studied using gated equilibrium radionuclide angiography (EQ-EF). In the normals, during exercise, EF increased by a mean of 25% of the resting value, with an increase of no less than 11%. The exercise-limiting symptom in patients with coronary artery disease was angina pectoris in 20 and fatique in the other 20 patients. In the angina patients, there was a mean decrease in EF of 20%, and in the other coronary artery disease patients ejection fraction change little. Only two patients with coronary artery disease increased from a normal resting value to peak exercise by more than 11%, and they had isolated right coronary lesions. An "overshoot" elevation of ejection fraction above resting levels was demonstrated following termination of exercise in most patients. The patients with a significant fall in exercise ejection fraction more frequently had abnormal exercise-induced ECG changes as well as abnormal left ventriculograms and more severe coronary artery disease at cardiac catheterization than the patients with little change in ejection fraction. We conclude that 1) normals could be separated from most patients with significant coronary artery disease in this study population; 2) ejection fraction must be measured at maximal exercise for it to have diagnostic value, since there could be normal rise before and after peak exercise and an abnormal response missed; and 3) the ejection fraction response to exercise reflects the severity of the underlying coronary artery disease. The described patterns of exercise-induced changes in left ventricular ejection fraction are important to consider when using this new technique to diagnose and evaluate patients with coronary artery disease.

Abstract

In order to compare the three non-invasive exercise tests Ecg, Thallium myocardial perfusion imaging and radionuclide angiography in the diagnosis of coronary artery disease, the results of these tests in a consecutive series of 30 patients and 14 controls were analyzed. In all 88 symptom-limited exercise tests a significantly higher double product (heart rate x systolic blood pressure, mm Hg/min) was reached on a treadmill test (for Ecg and Thallium scintigraphy) as compared to the supine bicycle ergometer exercise (for radionuclide angiography: 243.1 +/- 61.1 vs. 215.2 +/- 46.5 x 10(2) (p less than 0.01). Considering all 132 diagnostic tests the overall sensitivity for rest/exercise Ecg was 67%, for Thallium scans 77%, for both combined 83% and for the ejection fraction response to exercise determined by radionuclide angiography 97%. If only the exercise response was considered, the corresponding sensitivity values were 60% (Ecg), 47% (Thallium scans), 70% (both tests combined) and 97% (radionuclide angiography). The specificity for coronary artery disease was determined to be 79% for Ecg, 86% for Thallium scintigraphy, 64% for Ecg/Thallium scans and 71% for radionuclide angiography. The most common reason for a false-positive result in all tests was found to be the diagnosis of cardiomyopathy, whereas most false-negative results were seen in patients with single vessel right coronary artery disease. Based on these results, the clinical implications of the three non-invasive tests in the diagnosis of coronary artery disease are discussed.

Abstract

Forty asymptomatic male patients at low risk for cardiovascular disease completed maximal treadmill testing. Electrocardiograms from leads CC5, CM5, V5, Yh and Z were recorded across multiple pretest, exercise and recovery conditions. ECG waveforms were subsequently digitized, averaged and processed to provide Q-, R-, S- and T-wave amplitudes, ST-segment means and slopes, and QS- and RT-interval durations. Average R-wave amplitude increased during early exercise and then dramatically decreased to maximum effort. Average S-wave amplitude became greater as exercise progressed. Average J junction was slightly positive before exercise, became negative during exercise (except lead Z) and returned to zero after exercise. The ST-segment slope increased dramatically with progressive exercise. The response of T-wave amplitude, RT and QS intervals are also described. Separately, 22 asymptomatic male subjects each completed two maximal treadmill tests 2 weeks apart. ECG data acquisition and processing were similar to those noted above. Pooled, within-subject estimates of variability were computed for the ECG leads, ECG measurements and protocol conditions. These variability estimates are useful for interpreting ECG responses to exercise testing.

Abstract

This study presents the results of maximal treadmill testing and cardiac catheterization in 40 asymptomatic and apparently healthy men with acquired right bundle-branch block. Eight of the men had significant angiographic coronary artery disease, and six of the eight only had single-vessel disease. The 40 men had normal maximal oxygen consumptions, normal maximal heart rates, and normal maximal blood pressure responses; none of the men had abnormal ST-segment changes in response to maximal treadmill testing. Thus, the sensitivity of exercise testing for coronary artery disease in men with right bundle branch block is uncertain. However, the apparently high specificity of exercise testing demonstrated by this study necessitates further evaluation for coronary artery disease in men with right bundle branch block who develop abnormal ST-segment depression in response to exercise testing.

Abstract

In summary, near-maximal or maximal exercise testing has a sensitivity of approximately 60% and a specificity of approximately 90% for coronary atherosclerotic heart disease. When screening asympatomatic men with exercise testing, an abnormal response identifies a group of men at very high risk for coronary artery disease. However, the predictive value limitations are obvious and the false-positive problem must be realized. At present, there is no second line of noninvasive studies that can separate an exercise-test false positive from a true positive with certainty. Risk-factor consideration may help separate them; The sensitivity limitations of exercise testing must be especially considered when evaluating people at high risk for CAD. An abnormal test response does not absolutely predict the presence of CAD and a normal response does not rule out its possibility. In appropriate instances where coronary angiography can be performed at minimal risk and when it is justified for reasons of public safety or individual well-being, this procedure can give a reasonably definitive answer. Creation of iatrogenic "cardiac cripples" can be the most common complication of screening tests and should be avoided. Therefore, good clinical judgment needs to be used in conjunction with any screening test.

Abstract

Cardiac catheterization was used to evaluate 298 asymptomatic, apparently healthy aircrewmen with electrocardiographic abnormalities. These men were identified from annual electrocardiograms and exercise tests used to screen for latent heart disease. Data from 27 additional symptomatic aircrewmen who underwent cardiac catheterization because of mild probable angina pectoris are also included. The men were grouped according to major reason for cardiac catheterization. The order of groups by increasing prevalence of coronary artery disease was as follows: abnormal treadmill test (labile lead only), supraventricular tachycardia, right bundle branch block, left bundle branch block, abnormal treadmill test, ventricular irritability, probable infarct and angina. Approximately 60 percent of the men were completely free of angiographic coronary artery disease. Risk factors and other possible causes for the electrocardiographic abnormalities are discussed. The electrocardiographic abnormalities studied have a poorer predictive value for coronary artery disease in asymptomatic apparently healthy men than in a hospital or clinic population.

Abstract

Heart rates, blood pressures, and functional responses to submaximal, maximal and postexertional treadmill testing are presented for a group of 704 healthy, asymptomatic aircrewmen referred to the USAF School of Aerospace Medicine. The indicated measurements are individually described by the use of percentiles. These data provide the practicing clinician with an accurate and complete description of the response of healthy men to treadmill exercise.

Abstract

Unstable angina pectoris, Prinzmetal variant angina, and ischemic heart disease with normal coronary arteries, are three unique syndromes of ischemic heart disease that have recently become better understood. With the recognition of their manifestations, the combination of modern medical techniques and collaborative epidemiological studies should eventually lead to their early diagnosis, optimal treatment, and possible prevention.

Abstract

The data regarding the effect of physical of physical conditioning on the progression of myocardial is chemia, although suggestive of a favorable influence, are in no way definitive. Efforts to alter the physical activity habits of our population should not supersede efforts directed to alter the major risk factors. The emphasis in the prevention of coronary atherosclerotic heart disease for the general public should be on the well established cardinal risk factors, that is, hypercholesterolemia, hypertension, and cigarette smoking. The National Postinfarction Rehabilitation Study, when completed, may demonstrate how physical conditioning influences the progression of myocardial ischemia. However, "moderate activity is a part of a balanced satisfying living and is the safe and sane hygienic prescription of the thoughtful physician for his patients, the high risk and the healthy alike.

Abstract

This study presents the results of maximal treadmill testing and coronary angiography in 31 asymptomatic USAF aircrewmen with acquired left bundle branch block. There were two subgroups: 26 men with normal coronary angiography and five men with significant angiographic coronary angiography and five men with significant angiographic coronary artery disease. The mean amount of maximal ST-segment depression induced by treadmill exercise was --0.5 mv. for both groups and the range in the normal subgroup was --0.3 to --1.0 mv. No significant differences were found between the groups. We concluded that apparently healthy, asymptomatic men with acquired left bundle branch block can have considerable ST-segment depression in response to maximal treadmill testing and that their ST-segment response cannot be used to make diagnostic decisions about them.

Abstract

A new continuous treadmill protocol (USAFSAM) has been designed using a constant treadmill speed (3.3 miles/hour) and regular equal increments in treadmill grade (5%/3min). The constant treadmill speed requires only initial adaptation in patient stride, reduces technician adjustments and produces less electrocardiographic motion artifact than do protocols using multiple or higher treadmill speeds, or both. The regular equal increments in treadmill grade are easy to implement and provide a larger number of work loads than do protocols that are discontinuous or require larger changes in work load. The USAFSAM protocol was compared with the older Balke-Ware protocol in 26 healthy men (aged 30 to 59 years). Each fasting subject completed two maximal treadmill tests from each protocol. Measurements included minute heart rate from the electrocardiogram, auscultatory blood pressures and oxygen consumption obtained with standard techniques. Similarities in between-protocol measurements for submaximal and maximal treadmill efforts were impressive; differences were small and unimportant. Further, both protocols showed equal reproducibility for the measurements noted. Importantly, time to maximal effort was reduced by 24% with the USAFSAM protocol. The USAFSAM treadmill protocol has since been used in more than 500 clinical and screening examinations, thus confirming its advantages and practicality for routine clinical stress testing. Normal reference values previously established for the Balke-Ware protocol are shown to apply to the new USAFSAM protocol as well.

Abstract

The application of epidemiological techniques to clinical cardiology has led to very significant advances in the diagnosis and treatment of coronary atherosclerosis. However, these epidemiological techniques almost necessitate the use of modern computer technology, including data base management systems, in the application of which medicine has lagged behind other areas. Businessmen have come to rely on computerized methods of data storage, retrieval, and analysis to sell commercial products and manage our finances--while their medical counterparts rely on imcomplete data in forgetful minds beset with bias and emotion to use powerful therapeutic tools in the treatment of patients. Hopefully, the next decade will see a new generation of clinical researchers who will combine epidemiology and computer technology for the improvement of health care delivery.

Abstract

Treadmill exercise testing identifies a group of men at high risk for coronary atherosclerotic heart disease. However, the predictive value and sensitivity limitations are obvious. An abnormal electrocardiographic response does not absolutely predict the presence of coronary atherosclerotic heart disease, and a normal response does not rule out this possibility. Thus in appropriate instances when the minimal risk of coronary angiography is justified this procedure can be used to determine the anatomic correlation of exercise-induced functional ST-segment changes.

Abstract

ST-segment depression and slope were compared in three lead systems (V5, CC5, and CM5) and in two groups of patients using both visual analysis of electrocardiographic paper and computerized techniques. Bipolar lead CC5 was found to be comparable to lead V5 when visual analysis of electrocardiographic recordings was utilized. Bipolar lead CM5 was found not to be comparable to lead V5 and to be less sensitive if classic criteria for slope were used. The technique of computerized analysis mad measurements of slope and amplitude to a reproducible level not possible with the standard technique. Statistically significant differences were found between the exercise electrocardiographic leads utilizing computerized electrocardiographic analysis . We conclude that computerized techniques of electrocardiographic analysis require new criteria for defining an abnormal repolarization response. The criteria must be specific for different electrocardiographic leads if the repolarization changes in these leads are to have comparable diagnostic significance.

Abstract

This study investigated the hypothesis that an individual's maximal oxygen consumption can be realistically predicted by the maximal time achieved in the Balke or Bruce treadmill protocols. The range of maximal oxygen consumption that can be expected for healthy individuals of any given age and activity was also evaluated. The maximal oxygen consumptions achieved by 79 men exercised using the Balke protocol and 77 men using the Bruce protocol were linearly regressed by a least-squares fit technique on maximal treadmill time and on age with activity status classified. Statistical analysis demonstrated an inadequate relationship for predicting maximal oxygen consumption from maximal treadmill time using either protocol. Also, maximal oxygen consumption correlated poorly with age even though activity status was considered. These findings make the nomogram for predicting an individual's functional aerobic impairment a clinical technique of questionable value. Since maximal oxygen consumption can only be grossly estimated from the maximal time performed in the Bruce or Balke protocols, there is no necessity to use them in preference to other clinically acceptable protocols.

Abstract

A 45-year-old asymptomatic aircrewman is presented who developed an abnormal ST segment response to maximal treadmill testing after normal responses for 3 previous years. Coronary angiography performed after his abnormal stress test reveled no change from a previously normal study. It has been demostrated that serially performing exercise tests can increase the sensitivity of detecting latent coronary artery disease. The importance of the case report is to demonstrate that the change from a normal exercise test to an abnormal one does not absolutely indicate that an individual has a coronary artery disease and that it is mandatory to search for other possible causes. Further studies will be required to determine the significance of such serial changes.